1. A 3D model rendering method, comprising: calculating, in a diffuse reflection illumination situation simulated by hardware, dot product operation results of a light vector and a normal line vector of each vertex on a surface of a 3D model, the light vector corresponding to the diffuse reflection illumination, and converting the dot product operation results of each vertex to corresponding UV coordinate values; drawing, according to a preset correspondence between UV coordinate values and a color value of a 3D model basic texture after receiving light, a gradient map having a color value corresponding to the UV coordinate values of the each vertex; and covering the surface of the 3D model with the gradient map.