Abstract: Pseudo-thermal light is a regular source for correlated imaging. Compared to entangled bi-photon source, it can be easily obtained and put to use in experiment. Pseudo-thermal light and entangled bi-photon are similar in some particular ways, especially in photon statistics which is the key to correlated calculation. A quantum state is classical if it is a coherent state or a classically-random mixture of coherent states. Thus the zero-mean Gaussian state can be used to describe the phase-insensitive coherence propagation of pseudo-thermal light. Based on this model, semi-classical photo-detection theory of pseudo-thermal light can be build, correlation function of signal path and reference path can be derived. So that the resolution and contrast of ghost image and view of GI system can be analyzed.