Considering that the internal force and displacement of the monolithic lock chamber structure are greatly affected by the height of the lock chamber，this study investigates the internal force and displacement of the monolithic lock chamber structure with a large height-width ratio by the finite-element analysis method. The conclusions drawn are as follows：1）When the height-width ratio exceeds a certain value，the positive bending moment at the root of the side pier of the bottom plate of the monolithic lock chamber is larger than the negative bending moment in the middle of the bottom plate span，and the thickness of the bottom plate is determined by the positive bending moment. 2）When the height-width ratio is less than that value，the trend is just the opposite. 3）For a lock chamber structure with a large height-width ratio，setting a heel plate or an unloading plate behind the lock wall can reduce the positive bending moment at the root of the side pier of the bottom plate，increase the negative bending moment in the middle of the span，and ultimately reduce the displacement of the lock wall. In this way，a more uniform force on the bottom plate allows the thickness of the bottom plate to be reduced to optimize the design and save the cost.