To reduce crewmembers’ error and increase the safety of ships’ navigation, a recognition system of collision risks among multiple ships is newly-developed. By using ships’ navigational information such as AIS data, an algorithm to calculate collision risks among multiple ships is newly-designed. Collision risks of multiple ships can be estimated considering ships’ position and course of now and future by using fuzzy algorithm. To evaluate the performance of new system, replay simulation is carried out by using actual AIS data of actual collision accident in Korea. In this paper, main features of the monitoring system of collision risks and the results of replay simulation are discussed.