The invention discloses a system for detecting cotton rolling quality. The system comprises an image acquisition module, a computer and a hollow cotton sample putting platform, wherein an illuminating device is arranged in the cotton sample putting platform, and an optical glass plate is used as the top panel of the sample putting platform; the image acquisition module is arranged in the cotton sample putting platform, and a signal output end of the image acquisition module is connected with the computer through a digital image acquisition card. A cotton sample is irradiated by different wave lengths of light which is produced by the illuminating device, an image which is generated when the surface of the cotton sample is irradiated by the different wave lengths of light is shot by a CCD (Charge Coupled Device) camera, the image is transmitted to the computer through the digital image acquisition card to be analyzed and judged, exterior form and texture data, defect types and quantity data are obtained from a picture, an optimized weight value is calculated through machine learning, and a cotton rolling quality grade is calculated by an European distance judgment method according to cotton rolling quality index requirements in national standards GB1103-2012.