At present,the research on waterstop is mostly in the layout,design,and construction,while that on the stress capacity and deformation performance of waterstop under the working state of the gate is less. Moreover,most of the research on the waterstop performance is only for the waterstop itself. In actual engineering,the waterstop is fixed on the ship lock and is jointly affected by the water head. Therefore,it is necessary to consider the force when the waterstop is connected to the ship lock. Taking the 34 m-entrance triangular gate in the Yuxi ship lock expansion and reconstruction project as an example,we select two actual working conditions and two additional working conditions to conduct finite element simulation on the waterstop and the gate as a whole and analyze the working state,stress and deformation performance under each working condition. The result shows that the strength of the waterstop meets the requirements. The bottom waterstop and the side horn waterstop are in a compressed state,and the deformation performance is favorable. The middle horn waterstop plays a positive role in restraining the expansion of the gap.