The position sensitive detector（PSD） can be used for many types of precision and contactless dgmatic distance detection.The most important problem to use the PSD is how to overcome the disturbance influence of background light acting on the PSD.Based on the PSD principle

it is found that the output signal of PSD is nonlinear when there exist background light.A novel method which employs proportional-integral-derivative（PID） control the drivingpower of laser to realize background light compensation is presented

and the PID hardware circuit is designed as well.The experiments and application of PSD show that this method can eliminate the disturbance of the background light and the practicability of PSD is also increased.