Vegetation clumping index is required for canopy reflectance modeling and leaf area index (LAI) retrieval. Frequently used is the average clumping index. The angle effect is normalized in the definition of average clumping index. Clumping index angular distribution with different canopy spatial pattern and the same architectural features of single plant is modeled and analyzed in this paper. The real structure of single plant and the canopy spatial pattern are simulated by modified L-systems. The gap fraction is calculated by Radiosity-Graphics combined Model (RGM) and the clumping index is calculated through a formula which is derived from Nilson's classic formula to solving gap fraction. It can be seen from the comparison of gap fraction of six scenes that the maximum is appeared in the direction of zenith and the shape between forward and backward is roughly symmetrical. It can be seen from the comparison of clumping index of six scenes that the maximum is not always appeared in the direction of zenith and the shape between forward and backward is not always roughly symmetrical. The results indicate that the asymmetry of canopy spatial pattern will bring the asymmetry of the clumping index angular distribution and the clumping index angular distribution depends on both the architectural features of single plant and the canopy spatial pattern.