In this paper, the reliability of welded structure with an embedded elliptical crack was calculated by using three dimensional stochastic finite element method. This method has overcome the shortcomings of conservative results in safety assessment with deterministic fracture mechanics method. The calculation of reliability was based on three dimensional perturbation stochastic finite element program which was developed by ourselves. The effects of variables (such as fracture toughness K IC , load P, the ratio of minor axis to major axis a/c) on the structure reliability were also discussed. The calculation results indicate that among the three variables (K IC ,P, a/c) , the fracture toughness K IC has the greatest effect on the structure reliability. The next is external load P. The ratio of the a/c has lower effect on structure reliability than both K IC and P . The method has put forward a new way for safety assessment of welded structure with embedded elliptical cracks. This method has overcome the shortcomings of conservative results in safety assessment with deterministic fracture mechanics method. The calculation of reliability was based on three dimensional perturbation stochastic finite element program which was developed by ourselves. The effects of variables (such as fracture toughness K IC, load P, the ratio of minor axis to major axis a / c) on the structure reliability were also discussed. results indicate that among the three variables (K IC, P, a / c), the fracture toughness K IC has the greatest effect on the structure reliability. The next is external load P. The ratio of the a / c has lower effect on structure reliability than both K IC and P. The method has put forward a new way for safety assessment of welded structure with embedded elliptical cr acks.