The flow field structure of compound channel is more complex. this paper simulated the compound open-channel flows based on reynolds stress model (RSM) and finite volume method (FVM) and also used the coupled solver. It apply Roe averaged flux difference splitting (Roe-FDS) to discretizing flux. The comparison between numerical results and experimental data showed a very good agreement. Finally, the hydraulic characteristics of the cross-section of the compound channel was analyzed.