Abstract: The actual water-saving efficiency of water-saving locks is often lower than the theoretical value due to variations in the actual area of water-saving basins and the influence of residual heads during filling and emptying, which affects the efficient utilization of regional water resources. Based on the principle of water balance, this study establishes a computational model for determining the actual water-saving rate, incorporating both the actual areas of multi-level water-saving basins and the residual heads during filling and emptying. Corresponding mathematical formulas are derived, and a supporting calculation program is developed. The results show that the proposed formula for calculating the actual water-saving rate of multi-level water-saving locks is consistent with standard computational outcomes. A case study demonstrates that when the area ratio of one water-saving basin to the lock chamber increases from 0.2 to 2, the maximum water level difference in that basin decreases significantly from 8.84m to 2.45m, while the maximum water level differences in other basins slightly decrease from 4.72m to 3.87m, and the overall water-saving rate increases from 58.08% to 65.56%. Additionally, when the residual head during filling or emptying in one basin increases from 0.2m to 2m, the maximum water level difference in that basin changes from 4.09m to 3.43m, while in other basins it changes from 4.09m to 4.27m, with the water-saving rate varying from 63.63% to 62.07%.