The navigable building of Longtan hydropower station is a two-stage vertical ship lift with an intermediate channel，and the designed ship type is a 1 000 t-class mobile barge. By the method of physical model test，the experiment of ship out of the Longtan second stage ship lift chamber is carried out to study the hydraulic characteristics such as the water surface fluctuation in the chamber，the ship squat，and the force of the docking locking mechanism. The results indicate that from the perspective of ship lift docking safety and ship navigation safety，in order to meet the requirements of 1 000 t-class ship passing through the ship lift with a maximum draft of 2.4 m，the ships speed out of the chamber should be lower than or equal to 0.7 m/s when the ship chamber design water depth is 3.5 m.