In the most conventional structured light system, the camera must be perpendicular to the reference plane, and the connecting line between the exit pupil of the projecting system and the entrance pupil of the camera must be parallel to reference plane. Aiming at this problem, an unconstrained system configuration is built up, and the parallel and perpendicular constrained conditions are removed. A camera and a fringe projector consisting of the system can be posed freely depending on the objects and the purpose. Based on aforementioned unconstrained system, a new calibration method is presented. In the method, the spatial relationship of “projector-camera-reference plane” can be calibrated and reconstructed accurately, and therefore the important parameters—distance of two pupils and distance from camera to reference plane in the conventional structured light system can be obtained easily. Meanwhile, the new phase-height mapping relationship and height calculating formulas corresponding to the unconstrained system are derived. The experimental results prove that this method can obtain a range data in the accuracy of error about 0.1 mm.