The growth dynamics of Leymus chinensis, Stipa grandis, Agropyron michnoi, Artemisia frigida in Leymus chinensis+Stipa grandis degenerated community in the typical steppe of Inner Mongolia in one growing season were simulated and compared by the Logistic model. The results showed: ① Mathematical models of individual plants were determined according to the dynamic model of population. ② Growth of the plants was divided into four stages and the fast growing stages and the turning points of the four growing stages were also determined based on ecology theory and the Logistic model. ③Physical meaning of the model was explained. ④The periods of sustainable growth were determined and explained according to the ecology theory. Based on which the suggestions on grassland management and sustainable utilization were put forward. ⑤Growth of the four plants could be described with Logistic model. Simulation equations were:y= 0.2001+e2.032-0.060t， y= 1.2051+e2.608-0.042t， y= 0.1561+e1.858-0.040t，y= 3.1771+e2.770-0.077t respectively. The parameters in equations were effective and dependable, and all determinant coefficients exceeded 0.9. ⑥ Maximum growth rates were got through the model, it was A.frigida 6.112×10-2(g/(plant•d)) > S.grandis 1.267×10-2(g/(plant•d)) > L.chinensis 2995×10-3(g/(plant•d)) > A. michnoi 1.561×10-3(g/(plant•d)). Comparing the maximum growth rate of four plants, the value of maximum growth of A. frigida was 20 times of L. chinensis, 4.8 times of S. grandis and 39 times of A. michnoi. The life forms of L. chinensis, S. grandis and A. frigida were different, and their growth rates and growing curves were also different greatly. However the life form of A. michnoi and L. chinensis were same , and their growth rate showed the little difference with the maximum growth rate of L. chinensis being 1.9 times of that of A. michnoi. Also the two plants showed the similar growth dynamic in one growing season.