Spatial laser collimation system often uses the position sensitive device (PSD) as a photoelectric receiver unit, and a semiconductor laser as a light source. Because of the nonlinearity of PSD, the diffraction characteristics of laser light will result in different responses of collimation system at different spatial distances. To reduce the repeated calibration at different spatial distances during the operation of the spatial laser collimation system, we propose a simulation method of detecting the semiconductor laser spot position by PSD. In this method, the non-linear data of PSD target surface and the laser intensity distribution data are obtained with the design of the relevant optical systems, and the response of the PSD to the spot intensity center of gravity is simulated. Then, the simulation results are verified by experiment. The experimental results show that the simulation system designed in this paper can reproduce the actual PSD detection process, and the maximum error is only 0.026 mm in the relative displacement range of 0-4.5 mm.