With the development of modern manufacturing and testing technology, micro-vibration detection technology for rough metal surface plays an important role in many fields, including material analysis, nondestructive testing, and mechanical system dynamic analysis. The piezoelectric transducer has been widely used in detecting the micro-vibration on rough metal surface, but it is not available to be used on hot or corrosive surface, and hardly to achieve in-line detection for the limited working distance. Several interferometers have been developed for distant detection of micro-vibration, which work well on mirror surface in the laboratory, however, those interferometers can hardly be used to detect micro-vibration of rough metal surface due to the environmental noise and wavefront mismatch.A micro-vibration detection system based on differential two-wave mixing interference is proposed to meet the requirements of non-contact measurement for micro-vibration on rough metal surface. It provides a simple and elegant solution to these problems arising in the above interferometers, which results from the replacement of a conventional beam splitter with a dynamic holographic grating continuously recorded in a photorefractive crystal. The dynamic holographic grating is modulated by the interference fringe and presents the same distribution, but the change of dynamic holographic grating is available only when the time constant of photorefractive crystal is larger than the change frequency of the interference pattern, which contributes to the fact that the proposed system has the ability of low-frequency noise suppression in non-laboratory environment. The dynamic holographic grating in the photorefractive crystal adapts the reference wavefront to the signal beam, which enables the vibration measurement on rough surface of metal. To reduce the fluctuation of the beam intensity, electric noise, and single measurement error, the proposed system adopts two nonlinear Bi₁₂SiO₂₀ (BSO) photorefractive crystals to demodulate the vibration signals in the system. Two BSO photorefractive crystals are applied with high voltage of opposite polarity to obtain the dual-path signals with opposite polarity, by adopting differential processing to the dual-path signals, the noise insensitive to voltage polarity can be suppressed and the sensitivity to vibration can be improved. Simulation analysis is carried out to verify the feasibility of the proposed detection system, the simulation results show that the dynamic holographic grating is non-shifted or shifted by half of the grating period with respect to the interference fringes when the two BSO photorefractive crystals are applied with high voltage of positive or negative respectively, which contributes to the dual-path output beam intensity with an opposite polarity. By comparing the time domain diagram of vibration signal and output beam intensity in simulation, the capability of the proposed system to measure micro-vibration is affirmed. By calculating the amplitude of the output beam intensity corresponding to vibration signals of different amplitudes, the relationship between them can be achieved, from which an approximate linear relationship between the output beam intensity amplitude and the vibration signals amplitude can be known. To evaluate the noise suppression capability of the proposed system, Gaussian noise and high frequency noise is added to the laser intensity, the simulation result shows the added noise is effectively suppressed by the proposed system. A prototype has been built to further validate the feasibility of the proposed system. The vibration measurement experiment of a copper sheet connected to the piezoelectric transducer is carried out, and the measurement result of the proposed system is compared with the voltage applied to the piezoelectric transducer and the commercial laser vibrometer, the time domain diagram of them has an excellent consistency. Compared with the traditional single-path system, the sensitivity of the proposed system is doubled, the noise is suppressed, and the signal-to-noise ratio is increased from 27.47 dB to 30.83 dB. The relationship between the output voltage amplitude of the proposed system and the measured vibration amplitude can be obtained by applying various voltage amplitude to the piezoelectric transducer, which indicates that the proposed system has an exceptional linearity (the nonlinear error is 2.41% when the vibration amplitude is smaller than 40 nm). The vibration measurement with a frequency of 200 kHz is carried out to evaluate the capability of the proposed system for detecting the high frequency vibration, which is better than the maximum measuring frequency of commercial laser vibrometer (20 kHz). To verify the stability of the system proposed in this paper, the repeatability experiment was conducted, in which the copper sheet was measured 20 times and the measurement interval was 5 min, the relative residual error of each measured amplitude and average amplitude is calculated, the result of experiment shows that the peak to peak value and RMS value of the relative residual error in the proposed system are 4.11% and 1.42% respectively, which is better than the 8.69% and 3.07% in the traditional single-path system. The proposed detection system has high bandwidth and sensitivity with strong noise suppression ability, which provides an effective and feasible method for micro-vibration measurement of rough metal surface in an industrial environment.