Characteristics of vegetation succession and diversity were studied through field surveys of lands during a process of natural restoration in a pasture zone in the loess hilly region, and soil samples were taken for analysis of dynamic changes in soil organic carbon, alkalytic-nitrogen, total nitrogen, available phosphorus, and activities of urease, invertase, alkaline phosphates and catalase, and correlations of plant diversity with soil nutrients and enzyme activity as well. Results show that during 75 years of natural restoration, community succession began with annual herbs such as the Asteraceae (Artemisia scoparia) and the Chenopodiaceous (Corispermum chinganicum), which were gradually succeeded by perennial herbs, and finally by Stipa grandis and S. bungeana, which were the dominant species typical of the pasture zone. On the whole, a rising trend was observed of the number of species and a wavy but rising trend of the species diversity index and of soil nutrient and enzyme activities as well with increasing of natural restoration years, soil nutrient and enzyme activities increased with an increase of natural restoration years too. After 75 years of natural restoration, Margalef index, Shannon-Wienner index and Pielous index increased by 83.3%, 31.8% and 21.4%, respectively；soil organic carbon, alkaline nitrogen, total nitrogen and available phosphorus by 185.0%, 164.6%, 152.9% and 109.8%, respectively; and soil urease activity, invertase activity, alkaline phosphates activity, and catalase activity by 64.0%, 7.8%, 51.1% and 11.8%, respectively. Significant positive correlations were observed of soil nutrient and enzyme activities with Margalef and Shannon-Wienner index, but an insignificant one was with Pielous index.