Abstract: The climatic productivity of forage grass is calculated and the main restricting factors of impacting the climatic productivity are analyzed in north region of China The results show that the distribution tendency is decreasing gradually from east to west and from muth to north．The lowest value is smaller than 2000kg／hm²，but the highest value is higher than 30000kg／hm² The difference between the highest and the lowest is more than 15 times．Drought is the main climatic factor to influence the forage grass growth．So，developing artificial pastureland has a good prospect In the cropland shifting for tree planting，we have to put the water resource from cropland shifting into stock-raising (forest)to guarantee stock-raising(forest)production to be sustainable，high effective and stably developed．