To study the influence of nonlinear contact between structure and anchored rock mass on the seismic performance of a lock head under earthquake, taking the first stage lock head of a double-line five-stage ship lock as an example, a three-dimensional finite element model for the dynamic interaction of reservoir water-structure-anchor-bedrock was established in the finite element software ADINA. The various contact problems in the lock head structure were simulated by the nonlinear contact elements based on constraint function. The dynamic responses of the lock head structure, the distribution law of the anchor force, and the contact state of different contact surfaces under the design earthquake were analyzed by time-history analytical method. The results show that the piers on each side of the lock head are deformed to the side of the navigation channel under the design earthquake, and the displacement increases along the height direction. The maximum axial tensile stress of the anchor is less than its tensile strength. The upper parts of the contact surfaces between different contact pairs are repeatedly opening and closing. The maximum opening of the contact surface increases with elevation. At the end of the earthquake, the contact surface is restored to the state before earthquake. Therefore, the structural deformation, structural stress, anchor stress and contact surface contact state of the lock head all meet specification requirements under the design earthquake with good seismic capacity.