Based on the diffusion theory,a computational model is developed to deal with the problem of light transporting in biological tissues irradiated by arbitrary light source.According to the numerical calculation,the influence of convergence angle on the light field in biological tissues and light field reflected from biological tissues are discussed.Results show that with the increase of the convergence angle,light field in biological tissues and the reflectance enhanced in the beginning,after reaching the peak value,its intensity decrease quickly and the position of its maximum deflects from central position.