Abstract: The transformed martensite of dual-phase steel during the cooling stage of spot welding can make the weld nugget very brittle and result in interfacial fracture which was inspected by destructive methods.This failure mode can reduce the static strength and fatigue life of the weld.1.4 mm DP600 sheets were taken as an example, percentage of residual area in the whole nugget is used to evaluate the interfacial fracture magnitude.Then orthogonal test is used to analyze the influence of welding parameters on fracture magnitude. After single factor analysis, it can be concluded that the welding current is the most important factor that influence the welding magnitude.Using interaction analysis, the optimized welding parameters can be obtained.Experiments are conducted to validate that the modified welding parameters can reduce interfacial fracture magnitude effectively.