In order to understanding the characteristics and evolution trend of Caragana intermedia plantation herbaceous vegetation systematically and the response of soil nutrients in desert steppe, we used spatiotemporal substitution method, toke natural meadow as control, constructed three C. intermedia age as research sequence, and investigated inside and outside of different soil vegetation and shrubs and analyzed the relationship between them. The results showed that: （1）with the increasing of the planting years of C. intermedia, different groups of plants showed different trends to the overall important values: a significant increase in grasses, a significantly reduce in legume, and the weed species increase after the first decrease.（2） α diversity: the biodiversity index including Richness (S) Shannon Wiener index (H) had a highest value in 16a outside shrub (P<0.01). Evenness index (J) and Dominance index (P) did not showed significant trend in different stand ages. （3） β diversity: The change of Cody index（β_c）and MorisitaHorn(CMH) similarity index indicated that: the species of 16 a, 25 a and 37 a were quite different, while the differences were relatively small between 25 a and 37 a. The composition between 37 a Caragana forest and natural grassland species were similar. The β_ws index had the highest value in 25 a. （4）There was a significant “fertile island effect” of soil carbon and nitrogen in Caragana intermedia forest. The soil organic carbon had a significantly influence on community group for different artificial Caragana forest. The effect of soil nitrogen on plant diversity was not significant in shrubs interior while was significant in shrubs external. The study illustrated that: the positive effect of soil nutrient succession could improve the plant diversity in C. intermedia forest and enhance the degree of replacement of plant species. However, plant community succession had a trend from presence to natural meadow on later (37 a). The vegetation succession direction of C. intermedia forest was uncertain.