Abstract: Based on the virtual crack closure technology (VCCT), by using the method of single variable control changes, the numerical model is established in the light of the symmetric double edge crack in thin-walled cylindrical shell by symmetrical concentrated force. The crack tip energy release rate is obtained. The effect of the Zr-4 alloy cladding tube prefabricated crack length and external load on the stress intensity factor is analyzed. The approximate formula of stress intensity factor (SIF) was obtained by using the flexibility method. The validation results are in good agreement with the numerical results.