Abstract: In order to achieve synchronous transmission in multimode optical fiber communication,a light injected multimode semiconductor laser open-loop chaotic communication system was constructed,and its performance was numerically simulated.The results show that multimode semiconductor laser chaotic communication system is able to achieve complete synchronization if selecting appropriate system parameters.Corresponding modes of transmitted laser diode(T-LD) and received laser diode(R-LD) can achieve complete synchronization,and the system has a good tolerance to the internal parameter mismatch between T-LD and R-LD.