A split Monte Carlo (SMC) algorithm, based on the Phong's model, for the estimation of the impulse response on the infrared indoor channels is presented. It can be applied to the indoor channel including various reflection patterns, includi ng diffuse, mirror and other non_Lambert reflections.The simulation of the indoo r optical channel by SMC method based on the Phong's model can benefit significa ntly the design of high performance infrared systems. The calculation is much fa ster than the classical deterministic method, and the speed advantage is more ob vious at a large number of reflections.