The principle and the realizing method of coaxial degree automatic detecting system are briefly introduced. A microcomputer is the center of the coaxial degree automatic detecting system. The spare part to be detected is fixed on the rotating work desk by a clamp. When the work desk rotates around a circle, the system will set 72 sampling points on the circumference of a spare part to be detected. So the accuracy will be enhanced hugely than by the way of manual detecting. Therefore the system possesses very large practical value. It is suitable to spread it in the detecting field.