Abstract: For a portable structured light system, it must be easy to use and flexible. So the inconvenient and expensive equipment for calibration such as two or three orthogonal planes or extra fixed equipment should not be considered. For the purpose of fast 3D acquisition, the projection matrices of a portable structured light system should be estimated. This paper proposes a flexible calibration method to meet the requirements of the portable structured light system through a surface plane. A calibration board is attached to the surface plane, and a reference pattern is also projected by an LCD projector onto the surface plane. The camera observes the surface plane at a few different positions. Then, the world-to-image point pairs for the camera and projector are obtained based on the cross ratio and epipolar geometry, and the system is thus calibrated. The experiments conducted for the proposed calibration method demonstrate its accuracy and robustness.