Abstract: In this paper an experiment in the application of LANDSAT MSS'digital image processing technique to classify the aquatic planes in the Honghu lake,China,as well as the necessary ground feature spectrum measurements and plant chlorophyll content determination techniques are introduced. In order to obtain the expected result of the computer aided classification different methods of digital image feature extraction have been tried,namely the ratio transformation,the biomass index transformation and the linear slicing of image intensity.The original images were digitally rectified by control points to a certain map projection system using a general polynomial approch scheme before the classification proceedure. Included in this paper are the resulting colour-assigned image and the thematic map of Honghu lake's aquatic plant-association distribution;list of area of different classes of aquatic plants and analysis of the reliability of the resulting classification.These results might be useful for the lake management and investigation.