The fatigue performance of Q690D high strength steel and its welded joints were investigated, and the fatigue limit of Q690D base metal, butt joints and cruciform joints was discussed. The S-N design curves were fitted and compared with current design standards, thus fatigue properties and life were evaluated. The results indicate that the Q690D base metal shows higher fatigue resistance than plain steels, and the GB50017 design curve can be used to evaluate the fatigue life of butt joints with more than 300 thousand cycles, and has enough safety reserve. The S-N design curve of cruciform joints is in good agreement with the curve specified in AISC360. Scanning electron microscopy (SEM) was adopted to analyze the microscopic features of the fracture at different stages. The fatigue damage formula was obtained based on the assumption of zero plastic cumulative strain rate, and the effect of welding defects on fatigue damage of specimens was discussed. The fracture morphology can reflect the fatigue damage development process of the specimen, and the damage curve can also explain the formation mechanism of the fracture.