Objective Based on the physical principle of the heterodyne laser Doppler vibration measurement process, we analyze the measurement process of highfrequency and lowspeed movement in the presence of lowfrequency and highspeed background movement. In the process, the measurement noise generated by the presence of stray light exhibits chirp characteristics, with the effects and patterns of chirp noise explained. In response to the chirp noise, we propose a derivative preprocessing method for demodulation. The theoretical analysis shows the method exerts a significant effect on suppressing chirp noise, which is verified by simulations and experiments. Meanwhile, we set a heterodyne laser Doppler vibration measurement system with stray light and measure the target vibration. The normal method and derivative preprocessing method are adopted respectively for demodulation. The experimental results verify the existence of chirp noise and the effectiveness of the derivative preprocessing method in suppressing chirp noise, which decreases the chirp noise power by about 81.8%. The method can effectively reduce the influence of stray light on vibration measurement.Heterodyne laser Doppler vibration measurement technology is a widely adopted noncontact and nondestructive movement measurement method, with the advantages of fast response speed and high resolution. It has a strong detection ability for single frequency movement and can quickly identify the characteristic frequency of target movement. However,