In this paper

some analyses had been done by combining theory with practice based on a case study of a village which is located in Xi-Hai-Gu region

the very well-known poor region in our country.Soil and water loscaused by improper land use as usually saying

but why people do not use their land properly even today? The analysshow that. firstly the key problem refers to the population capacity of environment in an area; secondly

the central link is man-land relaticnship in land use

from which the equation

m_i=a_i×p_i can be summarized and it also predicates the population capacity of an area to be limited; and thirdly a perfect model of comprehensive controlling may be reached by two steps

the first is planting grasses

shrubs and trees and the second is controlling with engineering.