It is difficult to evaluate the large and multi-wave band optical imaging system performance in general testing ways. The wave front of optical system is the one of import parameters which represents imaging quality. The fundamental theories of information optics and phase retrieval have been applied. The point image of optical imaging system ( intensity point separate function ) was analyzed and computed. The wave font of optical system has been retrieved by the Fourier transform and an iterative approach. The related theory is discussed and algorithm model is presented. The compute software of phase retrieval has been made. The validity of compute software is proved by the computer imitation. The phase retrieval error is estimated and is less than 5% . The way which would reduce the phase retrieval error has been suggested when the technology is applied. Through detecting and analyzing the PSF imaging of optical system in the lab

the experimental results indicate that the computer software of phase retrieval is efficacious. So it is shown that the novel method is suited to retrieve wave front of optical systems.