The invention discloses a chlorophyll calculating method based on remote-sensing images and a water ecological model. The method comprises the steps of 1, based on remote-sensing image data, data preprocessing like radiometric calibration, atmospheric correction and image cropping and fusing is conducted; 2, a remote-sensing water quality inversion model is constructed, and respective inversion ofindexes like water temperature and chlorophyll concentration is achieved; 3, various index concentrations and future weather change which are obtained through inversion of the remote-sensing images are regarded as input conditions of the water ecological model, and the chlorophyll concentration dynamic change process of a water area environment is simulated within a future duration caused by change like nutritive substance conversion and algae growth and death under a future weather change condition. The chlorophyll calculating method is applicable to water environment monitoring and predicting, and has popularity and high calculation precision, chlorophyll concentration prediction and simulation of a large area of a drainage basin are achieved in real time under the condition of the limited monitoring site, and an integrated chlorophyll concentration predicting system integrating the remote-sensing images and the water ecological model can be formed.