The stress-release boot is always used in the fore and rear of SRM grain to relief stress-strain concentration under thermal loading. Since the debonded crack in the stress-release boot may be propagation unstable when the internal pressure entered the debonded crack cavity, the SRM with debonded cracks is very dangerous when it is lunched. So the stability analysis of the debonded cracks is very important to evaluate the defect grain structure integrity. In order to investigate the stability of debonded cracks in the stress-release boot of SRM grain during ignition pressurization, three-dimension (3-D) viscoelastic finite element models of the SRM grain with debonded cracks are established. The 3-D singular crack elements at the tips of cracks are developed to simulate the stress-release boot debonded crack propagation. And all the singular crack elements are included in the 3-D J-integral loop surface to improve the calculation precision. Along with the debonded crack propagation, the 3-D J-integrals of the debonded crack tips are respectively calculated to prejudge its expanding trend. The results show that the most dangerous situation will occur in the fore stress-release boot debonded cracks during the rocket being launched.