Identification of mature crops plays an important role in crop area estimation, agricultural production, and yield statistics. To provide a simple method for identification of crop at mature stage with remote sensing, the method based on normalized difference vegetation index (NDVI)-normalized spectral separation index (NSSI) space and Hue saturation value (HSV) transformation was proposed by using Sentinel-2A data. Fengyang County located in Chuzhou City, Anhui Province, was selected as study area. The pure pixel of photosynthetic vegetation, non-phototrophic vegetation and bare soil were estimated by using the NDVI-NSSI space firstly. Coverage of non-phototrophic vegetation and the distribution of mature crops were estimated by using spectral mixture analysis method. As wheat and rape had the same maturity period in the study area, HSV transformation was used to estimate the distribution of rape by using the Sentinel-2A data at the flowering stage of rape, and the mature wheat and rape was identified. The results were compared with ground observation data and auxiliary data, the accuracy of wheat and rape was 95.34%, and the Kappa coefficient was 0.904, which was higher than that of support vector machine method (accuracy was 91.66%, Kappa coefficient was 0.813) and the decision tree classification method (accuracy was 92.39%, Kappa coefficient was 0.838). The results indicated that non photosynthetic vegetation could be separated from soil background areas by using the NDVI-NSSI space and HSV transformation, and mature wheat and rape could be identified. The method can be used with less data demand and easy operated, which can provide idea and method for extracting bare soil during crop maturity and features with similar spectra to bare soil.