Based on the constraint-related fracture toughness determination method, the constraint-related residual strength of the nuclear power main pipeline with elliptical crack was calculated. Based on the Paris formula, the crack propagation life corresponding to different crack sizes was calculated. Further, based on the obtained constraint-related residual strength and crack propagation life, damage tolerance analysis was conducted for both cases of crack propagation along the depth direction and along the length direction, and damage tolerance assessment diagram was constructed. The results show that as the crack depth and crack length increase, the stress field at the crack tip increases, and the constraint-related residual strength decreases. According to the damage tolerance assessment diagram, it is clear to observe the residual strength and crack propagation life corresponding to different crack sizes. The damage tolerance analysis method was expaned from the field of aerospace equipment to the field of nuclear power, and the influence of constraints in damage tolerance analysis was incorporated.