Abstract: Oedaleus decorus asiaticus, mainly feeding on graminaceous, is one of most harmful grasshopper species in the Inner Mongolia.The effects of plant species on the growth and development of grasshopper reflect relationship between plant communities and grasshopper communities.In this study, by applying both the fields net and indoor independent feeding method, we compared the vitality index of three groups of O. asiaticus with different population densities, and quantitatively analyzed the effect of Stipa krylovii and Leymus chinensis on the growth and development of O. asiaticus. The result indicated that the relative growth rate of female which feed on S. krylovii is higher than which feed on L. chinensis. The plant coverage and the population density are main factors to affect the vitality of O. asiaticus. When the coverage of S. krylovii less than 25%, the vitality value increased slowly with the increase of coverage, when the coverage more than 25%, the vitality value increased rapidly. When the coverage of L. chinensis less than 25%, the vitality value decreased with the increase of coverage,when the coverage more than 25%, the vitality value positively related with the coverage. The vitality of O. asiaticus in S. krylovii is better than in L. chinensis. We also found that when density of grasshopper is less than 18 heads/m², the vitality value increases with the density. When we plant grass should adjust coverage of S. krylovii and L. chinensis, monitor density of O. asiaticus. The results provide an operational base for the rational distribution of grassland and harm reduction of grasshopper.