To investigate the evolutionary trend of leaf chlorophyll under water stress and accurately characterize the relationship between water stress intensity and chlorophyll content distribution , Chinese cabbage cultivated in greenhouses of Nanjing City was taken as the research object. Hyperspectral imaging technology was employed to obtain the spatiotemporal variation characteristics of the leaf chlorophyll distribution during the water stress process. The influence patterns of water stress on the distribution evolution and degradation process of chlorophyll in Chinese cabbage were systematically analyzed, and a sensitive indicator for water stress, namely the chlorophyll content degradation trend index (De), was proposed. The results show that compared with the greenness analysis of visible light images, hyperspectral images can rapidly and accurately capture the distribution and variation characteristics of plants’ chlorophyll content, enabling precise analysis of the degradation and evolution characteristics and regularity of plants’ chlorophyll under water stress. As water stress intensifies, leaves gradually turn yellow and senesce, and chlorophyll exhibits a gradual attenuation trend from the leaf edge to the leaf center; De shows good sensitivity and accuracy to water stress in Chinese cabbage plants, and it can be used for precise early warning of crops’ water stress and assessment of water shortage stages.