Owing to the limitation of optoelectric imaging systems’ pupil, it is inevitable to generate the diffraction effect in laser propagation; however, the laser energy distribution causing by the diffraction effect can directly affect the jamming effect to optoelectric imaging systems. First of all, we began with the basal Huygens-Fresnel principle and Fresnel-Kirchhoff diffraction formula in this paper, and deduced the laser energy distribution formula on the optoelectric imaging systems’ detector causing by the rectangular pupil, circular pupil and annulus pupil. Secondly, we simulated the laser energy distribution causing by the diffraction effect under the different pupil shapes, laser launch parameters, optical system’s parameters and optoelectric detector’s parameters, and investigated the laser energy distribution rule under the different conditions. The simulation results indicated that the range of intensity distribution increased with laser wavelength, laser incident energy, focal length and the size of pupil that also can affect the pattern of intensity distribution. The research fruits can provide the theoretical basis and technical support for evaluating laser jamming effect to optoelectric imaging systems.