Focusing on the problem that the traditional finite element analysis results of the cylindrical shell with prefabricated defects couldn't be applied on the engineering practice effectively due to the low computing precision of stress and strain, an equivalent crack analysis method with high redundancy was proposed. Treat the prefabricated defects as typical crack, and analyze the crack stability with the singular crack element method, then assess the structural integrity of the cylindrical shell with prefabricated defects according to the analytical results of the crack stability. The analysis result obtained through this new method is more reliable than the traditional finite element method, and it is practical in promoting the safety margin of the engineering design, especially for the prefabricated defects of cylindrical shell structure working in severe environment with high risk coefficient like linear explosive separation device of the missile.