When CCD was jammed by laser, the study of laser transmission was one of the most important parts for the jamming image simulation and jamming effect evaluation. The transmission of laser considering the reflection of the detection plane was studied. First, laser was focused by the lens. Because the detection plane of CCD was gridding-like structure, the focused laser reflected by the plane was modulated. According to the calculation of the laser transmission through the lens, the periodical spots appeared on the aperture plane. The simulation of the transmission proved that after the spots were reflected by the aperture plane, periodical spots image appeared on the detection plane. The experimental result was in accordance with the theory.