Abstract: Technologies currently used cannot effectively detect foreign fibers in cotton for their almost same appearance as the cotton fibers. In this paper, the method for detecting foreign fibers using micrographic NIR imaging was proposed. According to the method, the absorption characteristic discriminations between cotton fibers and foreign fibers at the near infrared band were transformed to image features discriminations. Then these discriminations were amplified through the micrographic lens on CCD. An image segmentation algorithm was selected for extracting foreign fiber objects from cotton background in image. The result indicated that the features of foreign fibers in the near infrared image were obvious and the conclusion was consistent with the fact. And it provided a feasible and an effective method to detect foreign fibers in cotton.