The ecological environment of the drainage area of the Lijiang river has been degenerating rapidly in

the past 30 years, and hence an experimental research on the long-term and short-term dynamic monitoring of

ecological environment variation of the drainage area of the Lijiang river was carried out by using the TM, ETM+

and MODIS. Rapid degeneration is attributed to two aspects: the headwater forest in the upper reaches of the

Lijiang river has been destroyed continually, and the riverbed sand layer has been mined out on the large scale.

This conclusion is based on information extraction, pattern analysis and recognition as well as comprehensive

explanation of TM and ETM+ images obtained from three periods of time (1986, 1998 and 2002) together with field

investigation. The variation law of water quality of the Lijiang river and the gross of the vegetation were

discovered, and the optimal monitor bands of MODIS were determined by spectrum analysis of water-body based on

pixels and calculation of MODIS-NDVI image data.