Abstract: Objective In the field of shipbuilding and marine engineering, to achieve the goal of energy conservation and emission reduction, improve the durability of engineering structures, reduce the weight of structures, and lower production and operation costs, the use of dissimilar materials is necessary. The explosive welded transition joint represented by steel/aluminum type is the most widely used in the shipbuilding industry, with aluminum alloy often used as the upper building material and steel as the main hull material. Methods A three-dimensional nonlinear finite element model is established using Patran software to numerically simulate the welded joint specimen. Fatigue tensile tests were conducted to study the fatigue performance of steel/aluminum transition joints. The nominal stress S-N curve and hot spot stress S-N curve of the steel/aluminum transition joint were obtained based on the nominal stress method and hot spot stress method, and compared with the fatigue resistance curves given in the specifications. Results For the nominal stress method, the life of the T-shaped welded joint of aluminum alloy recommended by the specifications is smaller than that of the actual welded joint specimen. For the hot spot stress method, when the hot spot stress of the cross-shaped welded joint of aluminum is greater than 76.80 MPa, the life recommended by the specifications is larger than that of the actual welded joint specimen. And when the hot spot stress is less than 76.80 MPa, the life recommended by the specifications is smaller than that of the actual welded joint specimen. Conclusion Therefore, the transition joint has a certain influence on the fatigue life of the welded joint specimen. The crack growth rate is obtained by using fracture mechanics methods, mainly based on the material structure, geometric dimensions of the crack, form and magnitude of the external load, to calculate the stress intensity factor of the crack. Based on the Paris formula, the crack growth model is obtained to guide the analysis of crack growth at the transition joint interface in the welded joint specimen.