Abstract: 【Objective】Research on interspecies relationships in agroforestry systems based on light environments is scarce. The agroforestry system solar radiation under trees act as energy of intercropping plants photosynthesis, which directly affects the intercrop of ecological process and the level of productivity. This research regarding the shade range and shade intensity of fruit trees is key to decide the intercropping system configuration and reasonable distance. However, the study of shade range of fruit trees is currently only expressed empirically.【Method】Therefore, based on the similarity principle of parallel rays, a model of an apple tree was constructed by reducing the size of a real tree by 50 times. This model was used to study the tree shade range. The range obtained via actual measurements was compared with that obtained via theoretical calculation using the solar altitude and solar azimuth, in order to optimize calculation formula. The optimized calculation formula is used to accureteiy calculate the shade range of apple trees in an agroforestry system.【Result】The theoretical apple-tree crown shading change, calculated from the solar altitude and solar azimuth, was compared with the shading change measured using a 3D apple tree model, in which the tree appears shrunken. The phenomenon neglects the half-shadow effect of an apple-tree crown. Thus, the traditional shading model is inaccurate in its description of crown shading change. The traditional shading model was fixed via the shading coordinates of measurement and the theoretical measurements. After using the fixed model, the accuracy of shading region, comparing with actual measurement, was enhanced 94%.【Conclusion】The theoretical shade range provided by an apple-tree crown(for 4, 5 and 6 years old apple trees)was deduced according to incoming principle of solar ray. The measured and theoretical shades of an apple-tree crown were comparatively analyzed. Then, the theoretical parameter of apple-tree crown shade was optimized. It was found that the improved mathematical model proposed in this study can accurately simulate the actual crown canopy shade range.