An unchanged zero-point is a main problem in the measurement process of dynamic angle measurement. For the designed dynamic angle measurement system with grating wedge-plate interferometer, a new method of determination of the zero-point of dynamic measurement is proposed. Special points of maximal and minimal optical path differences determined by interference using 360° natural angle standard are used as fixed zero-point of dynamic measurement. No additional optical path is needed by this method which makes the structure simple and operation easy. Experiments show that the positioning accuracy is better than 0.5".