In order to study the influence of the modulation method of the optical feedback effect of the microchip laser on the optical sensitivity of the laser, a method of driving piezoelectric transducer (PZT) with different modulation voltages and frequencies was used to tune the external cavity of the microchip laser, and the changes of the amplitude and sensitivity of the optical feedback fringe were observed. Numerical simulation and analysis based on the composite cavity equivalent model were conducted. The results show that by increasing the PZT modulation frequency so that it is closer to the relaxation oscillation frequency of the laser, the optical amplification effect becomes more obvious, and the output amplitude and PZT modulation frequency have the same trend. The PZT modulation frequency remains unchanged, and the 140 mA pump current is reduced to the light emission threshold current of about 100 mA, the relaxation oscillation peak will gradually approach the PZT frequency shift modulation amount, which can actively amplify the feedback light, and the gain can be as high as 105. The optical sensitivity is related to the distance between the PZT frequency shift amount and the relaxation oscillation peak. The closer the two are, the stronger the optical sensitivity is. The laser feedback system modulated by PZT has the advantages of lower cost and easy adjustment compared with acousto-optic modulation. This study provides a reference for jointly adjusting the pump current and PZT modulation amount to obtain optical feedback stripes with appropriate amplitude and low noise.