To improve the safety and efficiency when ships pass through a lock, a Cooperative Ship Formation System (CSFS) in the lock waterway is proposed. An improved ship formation structure with the combination of leader–follower and behaviour-based structure is designed, and the relevant control modes are described according to the process of ship formation passing through the lock. MilliMetre-Wave (MMW) radars are introduced for the perception of ship states. Moreover, speed control, stop control and distance keeping control methods are proposed, which are related to the distance keeping control mode, speed control mode, stop control mode, stop-finished mode and emergency stop mode. Finally, a real CSFS platform with three different engineering ships was implemented in the Gezhouba Lock waterway to verify the effectiveness of CSFS and proposed control methods. Several experimental tests were carried out with the CSFS platform. The experiment results show that: 1) the average tracking error of the distance keeping control is 2.43 m; 2) the average speed control error of the leading ship is 0.08 m/s; 3) the leading ship can stop at around 2.0 m to the stop line, and both the leading ship and the following ship can switch smoothly between the different control modes.