System calibration is one of the most important steps during SL (structured light) measurement that largely affects measurement results. To a panoramic SL system, the existing calibration methods, mainly adapted from general SL system, may fail when the common FOV (field of view) of the projector and camera is narrow. A calibration method using a planar mirror for omnidirectional SL system is proposed in this paper. Experimental results validate the effectiveness of this method.