Abstract: The grey system theory founded by professor Deng Julong is applied in the analysis,andas a result of which,eco-environment condition is recognized as the dominant factor influencing silt discharge amount at the upper reaches of the Fenhe River Reservoir.Theecological effects of water and soil conservation are analysed and predicted by three prediction models constructed with different time series.The fundamental measure for reducingsilt deposition in the reservoir is proposed as speeding up integrated control of water andsoil conservation at the upper reaches of the reservoir.

Key words: Dark coniferous forest, Forest litter, Chemical properties, Sejila Mountains, Tibet