Shipbuilding gantry crane is one of the crucial equipment for enhancing shipbuilding efficiency. Most of them feature large lifting capacity, significant height and span. However, there is a lack of refined research on the lifting performance, which is an important parameter of the crane. Taking a shipbuilding gantry crane as an example, its stress and displacement are analyzed in this paper by using the geometric nonlinear method. According to the national crane design specification and based on the stress intensity of the upper and lower trolleys at different lifting distances, the relationship between the lifting capacity of shipbuilding gantry cranes and the distances of the upper and lower trolleys is obtained. A more detailed lifting performance table of the crane is provided, which provides a theoretical basis for the rational use of large-tonnage shipbuilding gantry cranes and giving full play to their performance.