As one of the important fracture parameters, stress intensity factor plays an important role in the fracture analysis of engineering structures.Based on the concept of  J ₂-Integralintegral and the elementary theory of strength of materials,the stress intensity factors of the transverse crack of the six prismatic shell and the six prismatic shell with reinforcing rib are analyzed and solved. A method for solving the stress intensity factor of complex structure by using  J ₂-Integral method is presented.