The hydraulic floating ship lift adopted in Jinghong Hydropower Station has completely independent intellectual property in China.As a significant part of the water conveyance system of hydraulic floating ship lift,the profiled sudden enlargement steel structure is used to improve the flow state of the internal water channel to improve the conveyance efficiency.The profiled sudden enlargement steel structure is a large-volume profiled cavity with complicated working conditions,so beams are decorated both in and out of it to bear the water pressure.The mechanic analysis of working state and hydrostatic test status of the profiled sudden enlargement steel structure is conducted by the finite element analysis,results of which show that the structure strength meet the requirements.