A non-contact rotation angle measurement system based on a line laser, and a linear array CCD was established to extent the angle measuring scope of a scanning mirror. The structure and measurement principle of the measurement system were introduced. It calculates the rotational angle of the scanning mirror by the position of the laser spot on the linear CCD and extents the measuring scope by array mirrors with special design. To reduce the alignment requirements, the error was analyzed and a calibration measurement method with polynomial fitting was verified. A series of error sources that affect the measurement accuracy were analyzed and the total errors of the measurement system were calculated. Finally, the related measurement experiment was performed. Experimental results indicate that the measurement system can offer a resolution of 2.5, angular measurement range of 11 , and the precision of angular measurement is up to 3. Obtained results can satisfy the system requirements for non-contact, higher precision and wider measurement ranges.