In this paper,impulse response function based Monte Carlo method is used to simulate light distributions in different layers of biological tissues that is irradiated by various incident surface sources.The characteristics of light distribution in different transmitting depth and under different incident surface sources are analyzed comprehensively.The simulation results show that the impulse response function based Monte Carlo method has the potential of high computational efficiency and statistics stability.The dispersion of incident surface sources and the quantity of simulating photons in calculating impulse response functions are also discussed under different conditions.