During the restoration of plant cover in the degraded cropland,the existence of early successional dominant species was one of the most important factors influencing the process of vegetation succession.This experiment including two treatments:(1)natural regeneration (CT),and (2) sweetclover (Melilotus officinalis L.) planted at a density of 11.3 kg·hm^-2 (LT),was designed to explore the dynamic of plant community in the initial vegetation succession by introducing biennial legume species into the abandoned cropland located in the semiarid Loess Plateau of China.After 6-year-experiment,the results indicated that LT helped increase vegetation cover and accelerate the course of vegetation succession.For example,some later successional species like Artemisia frigida,Heteropappus altaicus and Stipa breviflora were showing up in LT in the third year of vegetation succession.Moreover,LT was beneficial to improve the productivity and stability of plant community.In contrast to CT,the averaged aboveground biomass of LT was higher by 67.90% across the experiment.Besides,LT helped increase the soil total nitrogen in the early stage of vegetation restoration.Compared with CT,the average soil total nitrogen in 2003～2005 was higher by 7.32% in LT.Across the experiment,the soil total nitrogen and available phosphorus were the limited factors influencing the plant community in both CT and LT.Therefore,the introduction of biennial legume specie is a better way to restore the plant community in the semiarid Loess Plateau,and the addition of phosphorus fertilizer during succession of plant community is also recommended.