Provided are a method and system for determining an optimal exposure of a structured light based 3D camera. The system includes a projecting means for illuminating a predetermined pattern on a target object, an image capturing means for capturing an image of the target object with the pattern projected, and a processing means for reconstructing 3D data for the target object by identifying the pattern of the captured images from the image capturing means. The system automatically determines an optimal exposure of the structured light based 3D camera system through analyzing the captured image of the target object.