Five degrees of freedom, inspection and flaw detection. The mechanical system of C-arm has five degrees of freedom, and its purpose is to detect flaw detection. As a tool of nondestructive testing technology, C-arm X-ray flaw detector consists of C-arm, swinging mechanism, rotating mechanism, lifting mechanism and walking mechanism. Five degrees of freedom are realized, that is, the semi-circular sliding, swinging, rotating, lifting and horizontal movement of the C-arm.