Aiming at the requirements of the rotational speed measurement of closed rotating machinery, a rotating speed test method based on vibration analysis is proposed. Due to the uneven distribution of the mechanical rotor mass, the rotor will inevitably produce a simple harmonic motion during the rotation process. And the frequency of the vibration is equal to the frequency of the rotor rotation, thereby converting the measurement of the rotor rotating speed to the frequency measurement of the rotor vibration. The vibration test sensor is used to pick up the mechanical vibration signal, and the vibration signal is converted into a voltage signal with a certain intensity through the signal conditioning circuit, and the voltage signal is collected and transmitted to the computer for processing by the AD data acquisition module. The Visual Basic 6.0 software platform is used to write the rotating speed test system based on the minimum condition system identification theory, and the collected vibration data is processed to calculate the rotational speed of the closed rotating machine. The software design flow chart with the speed test system is attached, and the field test experiment is carried out to analyze the feasibility and error of the test system.