Abstract: In order to recognize the defects in the solid motor,a new method integrating image moment invariants method and histogram analysis method was put forward.Firstly,the cracks were distinguished from other defects by using image moment invariants method to recognize the shapes of defects.Secondly,histogram analysis method was used to calculate the gray intervals of bubbles and slag inclusions,and then distinguish them.So defects in solid motor were recognized automatically.The problems such as low recognition efficiency and low veracity induced by manual defect recognition are thus resolved and the capability of solid motor is ensured.