【Objective】As an important agro-ecological region, the Weibei rainfed highland needs urgently measures to build up its soil fertility and improve its eco-environment because of its infertile soil and severe soil erosion. High in stress tolerance, leguminous green manure crops grow normally in severe ecological environment. Cultivation and incorporation of such crops may help reduce soil erosion as well as improving soil structure and soil fertility.【Method】In order to explore rules of changes in farmland soil nutrients and ecological stoichiometry characteristics as affected by cultivation and incorporation of green manure crops in summer fallow seasons, a field experiment was designed to have three different species of leguminous green manure crops [Mung bean (Phaseolus radiatus L.), soybean (Glycine max (L.) Merr. ) and Huai bean (Glycine ussuriensis Regel et Maack)], four nitrogen fertilization rates (N₀, 0 kg N hm^-2; N₁, 108 kg N hm^-2; N₂, 135 kg N hm^-2 and N₃, 162 kg N hm^-2) and three replicates for each treatment, laid out in a split plot design in a tract of farmland in the Weibei Rainfed Highland, and conducted for six years in a row. Soil samples were collected at the end of the experiment from each treatment for analysis of nutrient contents and eco-stoichiometric ratios of C:N, C:P and N:P.【Result】Results show that the long-term cultivation and incorporation of leguminous green manure crops improved soil organic carbon, total nitrogen, alkaline nitrogen contents significantly or by 4.47%~15.35%, 5.21%~6.25% and 11.00%~14.35%, respectively, as compared to CK (the fallow treatment), and the effects of Huai bean were the most obvious in all the treatments. Two weeks after the incorporation of green manure crops, soil total nitrogen, soil organic matter and alkaline nitrogen all increased in content, but the margin of the increase of the former was higher than that of the latter two. In the treatments with Huai bean, organic carbon, total nitrogen, alkaline nitrogen, total phosphorus and available phosphorus all increased significantly, either in a short term or a long term, indicating that the effect of the green manure crop of Huai bean on soil building is the most obvious. Huai bean, high in number of root nodules and in nitrogen content, is a crop widely cultivated in the local area. After the incorporation of a green manure crop into the soil, soil C:N declined for the first short period of time, but in the long run, soil C:N was increased, which is beneficial to the accumulation of soil organic matter and improvement of soil nutrient balance. The ratios of C:N, C:P and N:P in the experiment field are all quite low, because the soil is low in soil organic carbon and total nitrogen, but high in total phosphorus. Soil carbon and nitrogen are the two limiting soil nutrient elements in this region. In the process of improving soil fertility, it is essential to focus not only on dynamic changes of total carbon, nitrogen, phosphorus but also on nutrient balance, especially C:N. In the practice of agricultural production, it is a must to ensure soil N supply, and in addition, enough attention to input of organic materials in such ways as incorporating crop straw into soil and expanding application of organic manure, so as to maintain the balance of soil carbon and nitrogen.【Conclusion】Soil C:P and N:P is closely related to dynamics of soil carbon and nitrogen contents. Cultivation and incorporation of green manure crops in the summer fallow period significantly improves soil carbon and nitrogen status, and hence is an effective practice to build up soil fertility in the Weibei rainfed highland.