Associated with the ecological survey of the Tumenjiang River Vally, on-the-spot investigations and observations about the functions of soil ecosystems were conducted and assessment criteria for the influences of topographic conditions on the function of soil ecosystems in the river valley were put forward, Results.obtained showed that (1) The ecological function was weakened with the increase of the altitude; The vertical differentiation of ecological function for the soils was in the orders: mountain dark brown earth>hilly dark brown earth>mountain brown coniferous, forest soil>mountain tundra soil and table land albic soil>high table land albic soil>low table albic soil; (2) The local climatic and biological conditions were influenced by topographical conditions; hydrothermal conditions were the main factors affecting ecological functions of the soils; deterioration of vegetative covEr and soil erosion promoted the degradation of soils; and (3) Number and kind of animal population could be used as the important criteria for assessment of soil ecosystems.