Digital Goniometer MAT-300 could be used for precision prisms measurement or polygon calibration without the standard prism gauge for comparison. The working principle is to use the autocollimator to detect the two surfaces of the testing angle respectively, and the rotary table consists of a precision air-bearing and multi-axes kinematics mounting plate, which would not induce any error during rotate the prism from face 1 to face 2, and assure the encoder read the pure prism angle value. The equipped high accurate encoder(with 0.1 acr-second resolution) to real-time read the angle rotating and directly shown on the software interface.