The invention relates to a cotton fiber color testing device. The device is characterized by comprising a sample frame, wherein optical glass is arranged at the bottom of the sample frame, the top ofthe sample frame is open, a sample is arranged in the sample frame, a sponge mat and an upper cover are sequentially arranged above the sample, and the upper cover and the sponge mat slide up and downin the sample frame. According to another technical scheme, the invention provides a cotton fiber color testing method. According to the new cotton fiber color testing analysis method and device, compared with existing cotton fiber color testing equipment, color indexes are improved in the three aspects that the influence of impurities on cotton fiber color testing is removed; a new color index ais added, and representation of fiber colors in a three-dimensional color space is truly realized; and variation coefficients of all color values of Rd, +b and a are added, and representation of non-uniformity of maturity isochromatic characteristics of each batch of cotton is benefited.