This paper studies the dynamic multicast traffic grooming problem and proposes a novel auxiliary grooming model.The layered graph model can represent current network resource states and is modified adaptively.On this grooming graph model,multicast routing and wavelength assignment can be realized at the same time.We propose a multicast traffic grooming algorithm(MGA),and the simulations show it has lower network blocking probability under the constraints of wavelength continuity and limited wavelength and transceiver resources.