The point spread function(PSF) of ghost imaging system is investigated. Taking the ghost imaging system of an axial moving target as an example, it’s PSF is derived in theory, and the numerical simulation and computer simulation experiment are carried out. Results show that the axial movement of target in signal light path leads to the decrease of imaging quality, and the greater the speed is, the worse the imaging quality will be. The imaging effect can be prejudeged by using the imaging quality of ghost imaging system analyzed with PSF method, which has a great advantage compared with the traditional quality evaluation method.