Abstract: There is inseparable connection between biomass of natural grass and climatic factor,but the effect of climatic factor on growth-development or biomass is not simple relationship of single climatic factor.During the different phase of plant growth- development, the effect of the same climatic factor has greatest difference.On the basis of predecessors＇research, the climatic factors are analyzed in different stages of natural grass growth-development,and relationship between the distribution in time and in space of biomass of natural grass and water-heat condition is also discussed.