In order to improve the modernization of textile production, single off-line testing will miss a lot of information of work-field. It is necessary to improve the yarn quality testing methods to make it more perfect. So the production will grow toward the rapid, high yield, high-quality. In this study, only a sensor that is Intelligent laser sensor is used to finish the yarn quality on line testing. Experimental device is easy to install and carry. It can print images and data at all times. The accurate information of equipment state and yarn can be got from the experimental curve and the trend figure, which improved the inspection efficiency and accuracy of yarn quality.