Taking ’Jinkang NO.1’ Chinese cabbage as experimental materials,the effects of shooting angle on digital indexes of canopy images and the relationships between digital indexes and soil inorganic nitrogen content,plant nitrogen nutrition indexes were was analyzed under six nitrogen levels.The results showed that the best angle between digital camera and Chinese cabbage canopy was 30°-60°.Among the digital indexes,the standardized green light G/（R+G+B） of Chinese cabbage canopy image had the best correlation with soil inorganic nitrogen content and nitrogen nutrition indexes,which could be used as the best digital index for the diagnosis of Nitrogen nutrition of Chinese cabbage.Linear equation model were established between G/（R+G+B） and soil inorganic nitrogen content,total N content in plant,total N content in leaf,nitrate concentration in petiole and SPAD.In conclusion,digital image processing technique can be used as a method of nitrogen nutrition diagnosis in Chinese cabbage,the G/（R+G+B） linear equation model of canopy image can be used to evaluate and predict the nitrogen nutrition of Chinese cabbage.