The modulation and demodulation technology of semiconductor laser self-mixing interference vibrometer is researched. With triangular wave modulation and DSP demodulation technology of self-mixing interference,a new type vibrometer is designed to achieve non-contact vibration measurement of a target. The theoretical model of the laser self-mixing interference vibrometer is analyzed and simulation and measurement error analysis are done using matlab. The modulation and demodulation technology of the vibrometer system and DSP-based data acquisition and processing system are researched. The vibrometer is small-sized,low-cost and easy to collimate,and can measure the object whose vibration frequency range arrives 5 kHz,and the vibration scope measuring accuracy may achieve 0.325 μm. The instrument can measure the vibration frequency and amplitude data of the vibration object and restore the vibration wave.