During the water level design process of lock with water saving basins （WSB），its an important part that to determine the water level and head of the WSB，and there are many influencing factors in the process. This paper derives and establishes calculation formulas for evaluating the water level and the water head of the single step lock with WSB，which integrates the total head of ship lock，the upper and lower stream water level variation，the number of the WSB levels and area of the WSB，and the remaining head. On the basis of formulas，the influence of factors such as the upper and lower stream water level variation，the number of the WSB levels and the area of the WSB on the water level and the water head of the WSB are analyzed. Finally，the water levels and water heads of difference WSB schemes are calculated and compared in a 60 m single-level ship lock，and a reasonable water level scheme of WSB is proposed.