Abstract: An AIS-based model for ship encounter situation identification and collision risk assessment is developed to monitor the ferry boats crossing main channel. The ship encounter scenarios are identified through examining the ship tracks. Fuzzy comprehensive evaluation is used to assess the collision risk. The process is accomplished in real time. The design is verified through processing the data set from the ferry Banqiao sailing in the Nanjing section of the Yangtze River. The experiment indicates that the situation of ship encountering can be rather complicated, especially when traffic is busy, which suggests the value of the research.