The uniformity and orthogonality are important technical indicators of photoelectric incremental encoders′ performance. The precision measuring of incremental encoders is an important link in development and manufacture of encoders. Traditional measurement of signal quality is based on time position and varied from the uniformity of rotating speed. The dynamic performance testing is incorrect with high speed and variable speed rotation. A testing method based on angle was proposed and corresponding system was established. The measured incremental encoder and a high-precision angular impulse generator were installed and rotated synchronously with a brushless DC motor; when measured incremental encoder output a signal edge, collected the data of the high precision angular generator and calculated the error. The detection error of the proposed system caused by uneven shaft rotating speed of the encoder shaft was greatly reduced. Measurements were carried out through encoders with periodical impulse output number 32 400, and was contrasted to the experiment based on time. The experimental results show that the system is free of the impacts of varying speed of driving motor, and is capable of improving the accuracy and efficiency of the incremental encoders testing. It was the proposed system that brings the batch production with great convenience.