Abstract: This author designs the random process between photons and crop canopy. A Monte Carlo model has been developed to simulate the Bi-directional Reflectance Distribution Function (BRDF) of crop canopy. Comparing Monte Carlo model to MCRM model, this paper analyzes the variations of different LAD and LAI of these two models and gives the reasonable explanation. It can be concluded that although there are some differences in BRDF value, the BRDF change trend with varying LAD and LAI reaches a good agreement. In the end using field measured BRDF data to validate Monte Carlo model, the results show that the simulated BRDF with Monte Carlo model is in good accordance to the field data. Therefore, Monte Carlo model can provide the effective validation tool of other forward BRDF simulation models of crop canopy.