To get influential parameters to represent hazardous factors of solid rocket motor, the various defects in solid rocket motor were generalized statistically, and the characters of shape, position and grey of debonding, slag inclusion, bubble, and cracks and so on were analyzed in detail. The grey feature analysis drew the law of grey change around the defects. The hazard effects of defects in the rocket motor in various position, surface and direction were analyzed. The research shows that the influential parameters to represent the hazardous factors are the geometric center of the defect, the surface area of the defects, the maximum diameter length and the angle between the maximum diameter and the axe.