The launching of land satellites makes it possible to make a quick and accurate study of land cover of a watershed, which is of great significance in hydrography.The present article takes Da-Wen River in the lower reaches of the Huang He River as an example, and selects seven kinds of typical land cover, mountains covered with dense forests, mountains covered with sparse forests, hills covered with grass and bush, hilly fields, plain fields, water and city. By the use of the digital data of films of the second land satellite of Oct.31, 1975 in 4 bands and the digital data of photograph of the third land satellite of April 1, 1978, MSS7, land cover of a watershed was analysed in a quantitative way and its was result compared with that of visual interpretation.