Abstract: We selected five vegetation restoration methods including mono-planting of Caragana korshinskii (UC), Agropyron cristatum (UA), and Hedysarum fruticosum (UH), mixed-planting of Agropyron cristatum and Hedysarum fruticosum (AC) and of Agropyron cristatum, Hedysarum fruticosum, Caragana korshinskii, and Elymus nutans (ACHE) to analyze the community structure and diversity of nirK-type soil denitrifying bacteria and their relationships with the soil physical and chemical factors. Bare land was used as a control (CK). There are significant differences in the composition of the soil nirK-type denitrifying bacteria. The Shannon index of the nirK gene is the highest under UH, followed by under UA, UC, AC and ACHE, and the lowest in CK with significant differences between the five methods. The sequence and phylogenetic analysis showed that the similarity of the nirK fragments to the nirK genes registered in GenBank was between 81% and 99%, and that they were mainly from Ochrobactrum, Rhizobium, and some other unidentified bacteria. These bacterial species accounted for more than 50% of the total fragments. Canonical correspondence and correlation analyses showed that the soil available phosphorus, pH, total nitrogen, total phosphorus and soil moisture had significant effects on the denitrifying bacterial communities, and there were very significant correlations among these five soil physical and chemical factors. It is suggested that interactions between the five soil physical and chemical factors played a decisive role in the population changes of the nirK-type denitrifying bacteria.