The water-saving ship lock can reduce the working head of each stage through classifying the total head. In addition to saving the water consumption，it is also conducive to solving the hydraulic problems of the high head ship lock. Therefore it is suitable for ship locks on rivers in western mountain areas of China. Based on the analyses of the operation principle of the water-saving ship lock，the calculation method of theoretical water saving rate and its variation with the step and area of water saving pools are studied in this paper，and the main factors affecting the water level classification of water-saving ship lock are summarized and analyzed. According to the characteristics of large variation of upstream water level，high design head，complex engineering layout conditions and operation modes，the variation laws of residual head in water saving operation are calculated on the navigation ship lock of Baise water control project on the Youjiang River in Guangxi. From the aspects of operation water level，and the step and area of the storage basins，the layout parameters of the storage basins and the water level classification method of the water-saving ship lock are proposed under large water level variation. Furthermore，the hydraulic indexes under different operation modes are simulated and calculated，and the scientific and reasonable classification of water level is proved.