Research on the waterway traffic flow modelling has been widely used in the formulation of waterway transportation regulations, navigation risk assessment, vessel traffic monitoring and organization. The fluency of one-way waterway transportation is proposed in this paper. By using the model, a simulation system is constructed on the basis of First Come First Served (FCFS) model. Monte Carlo simulations are carried out to see the performance of navigation efficiency. The vessels are generated randomly according to statistical characteristics on ship arrival rate and speed among others. Moreover, the safe distance is used to guarantee navigational safety. Based on the simulations, the relationships between traffic fluency and the parameters that are related with traffic efficiency, including channel length, vessel's arrival rate and vessel speed are analyzed. The results can provide a reference for vessel traffic organization and scheduling.