Abstract: In three-dimensional testing systems based on line-structured light, extracting the center of a line-structured light stripe quickly and accurately is a key problem. To extract the center of line-structured light with a length of 2 meter in a large field of view and strong noise background, an exaction method based on region of interest (ROI) is proposed. Firstly, ROI for image processing is defined by using statistic method, then Otsu method is used for threshold segmentation and barycenter method is used to exact the center within ROI. Experiments showed that the extracting time of a 12801024 sized picture of a line-structured light was about 47ms in Visual C ++6.0 by the proposed method and the extraction was proved accurate. The proposed method reduces the interference of strong background noise in large field of view and improves the extraction speed of line-structured light.