To deal with the problems like artificial steak untwisting, the low work efficiency and labor intensity in printing and dyeing industry in our country, meridian skew detection method based on machine vision is proposed. It greatly improves the efficiency of untwisting and precision. By using a CCD camera to obtain images of the fabric, the system uses the obtained images for Blob analysis. The analysis of the main process includes the extraction of image, image segmentation(the initial segmentation, morphology processing, etc.), and feature extraction. Experiments show that the method can detect the warp of skew, and has very high precision, can be used for vertical untwisting of machine.