Accurate estimation of reaso nable grassland yield is an important scientific basis in determining the carrying capacity .To maintain ecological balance of grassland ,a reasonable arrangement of animal husbandry has important theoretical and practical significances .There are three main approaches to estimate grass production:field measurement , meteoro-simulation model , and remote sensing .A large number of survey data are used to construct a mathematical model.The model is used to estimate grass production and then compared with other models for its reliability and accuracy .At last , the modelis applied to estimating forage production