Abstract: Fracture mechanisms of welding crater solidification cracking were analyzed and revealed by fracture mechanics involved physical quantity and finite element method. Non-dimensionalized method and orthogonal transformation were utilized to translate the weld-induced stress into the loading force used in the stress intensity factor calculation model. Numerical simulation model of the crater solidification crack based on the stress intensity factor were established. The thermal stress intensity factors, including opening, shearing and tearing of the cracks, were calculated and analyzed. The fracture mechanism of the crater solidification crack was further revealed and then verified by fractography. Results showed that the fracture mechanism of the crater solidification cracking was dominated by pull crack, while the cracking propagation was fastest under the sensitive temperature range between 1 100~1 000 °C, presenting a zigzag shape cracking orientation.