Abstract: An efficient model for computing the distribution of direct solar radiation in a maize canopy was developed. A virtual camera and a virtual canopy were used to complete the simulation at organ level, in which plant organ types were labeled by different colors. The virtual camera was used to take pictures of the virtual canopy from solar incident direction, with orthographic projection. The images were then used to compute the light distribution among individual plant organs by counting pixel numbers of each color type. The validities of the simulation results were evaluated from two aspects: simulation accuracy and computing time. The results showed that the simulation results agreed satisfactorily with those produced by a projection Z-buffer model(PZB) which had been validated by field experiments, but the computing time was much shorter than PZB model, and then was further decreased when introducing an algorithm to compute the minimum number of copied plants around the studied plant stand. Furthermore, the feasibility of simplifications of plant organs was discussed. The results showed that excessive simplifications resulted in increasing the simulation errors noticeably.