During measurement, the laser self-mixing interference is susceptible to noise interference, which affects the measurement’s accuracy and stability. Consequently, based on the use of dual-beam feedback to improve the signal-to-noise ratio of self-mixing interference signals, this paper aims to further reduce the system noise by incorporating the dual-polarization differential detection technology of random polarization laser self-mixing interference. Experimental results show that combining dual-beam feedback with dual-polarization differential technology can increase the signal-to-noise ratio of self-mixing interference signals by 7 dB. Therefore, the proposed method and technique have good application value in self-mixing interferometry.