In order to reduce the network load and improve the transmission efficiency of optical network in optical communication system.A theoretical method of all-optical multicast based on stimulated Raman scattering effect in photonic crystal fiber was proposed.The theoretical model of the method was established based on the analysis theory of forward transient stimulated Raman scattering effect in photonic crystal fiber,and the simulation results was analyzed by Matlab software.According to the theoretical model,the functional flow-process diagram was designed.The simulation results by Optisystem software show that the information carried by the output multicast light after all-optical multicast is consistent with the information carried by the original information light before multicast.The trajectory line of the simulated eye pattern is clear and the opening degree is good.The feasibility of the design method is verified.