In order to realize the high efficiency and harmlessness of textile fiber detection, the rapid detection method is provided to textile enterprises and market regulatory authority. In this paper, 281 samples of cotton/spandex blend are taken as the research object, and the influence of sample colors and fabric structures is analyzed. The near-infrared quantitative model of fiber content in cotton/spandex blended fabric is established by the partial least square method. To verify the accuracy of the model, the prediction is made based on 23 cotton/spandex samples. The predicted results are paired with the standard method SN/T 0464-2003 in t-test, and the conclusion that there are no significant differences between the two methods is obtained. The near-infrared method has been converted into the industry standard of inspection and quarantine and proved to be effective in practical application.