Abstract: In this paper, the dynamic models for livestock population in rangeland of Yanchi county were established by system dynamic method and grey system theory. With the computer process of model, several sensitive parameters such as total elimination coefficient of basal ewes,wether slaughter rate(C₆), percentage of killing Iambs (P₁)and rate of lamb fur (P₂) are found, by which, it is possible to control the development of Tan sheep and goat populations. The author considers that controlling livestosk population can raise the economic benefits.

Key words: Model, Livestock population, Sensitive parameter, crop water requirement, North Xinjiang., cotton, spatial-temporal distribution, water surplus deficit index