The integral lock head's floor easily appears cracks in the direction of water flow,which seriously harms the use safety of locks. The scheme of construction wide joints can effectively improve the cracking problem of integral lock head floor . The paper first applied ANSYS software to set up model,carried out finite element analysis for lock head' structure and further researched the influence of wide construction joints on the stress and deformation of the floor.It converted the stress result into internal force and finally got the optimum closed time and location which could meet the engineering requirement so as to provide reference. The result can provide reference for the construction of integral lock head.