Abstract: Understanding the micro-mechanisms of soil nitrogen formation can provide useful information about the growth and recovery of microorganisms in an alpine meadow. In this study, soil samples were collected from the alpine meadow in Maqu from sites under four types of management; unfenced, enclosed, enclosed with fertilization, and enclosed with sowing. The number of soil nitrogen microorganism groups was determined by the plate colony count and MPN (most probable number) methods. The number of nitrogen bacterial groups decreased with increasing soil depth at all sites. The number of nitrogen bacterial groups was significantly higher in the 0-10 cm and the 10-20 cm soil layers (P<0.05) than in the 20-30 cm soil layer (1.23-4.03 times and 1.11-2.25 times that in the 20-30 cm soil layer, respectively). There were also significant differences in abundance among the microorganism groups. The groups were ranked, from most abundant to least abundant, as follows: ammonifiers>denitrifying bacteria>nitrifiers>aerobic nitrogen-fixing bacteria (aerobic NFB)>anaerobic nitrogen-fixing bacteria (anaerobic NFB). In the same soil layer, there were significant differences in the abundance of bacterial groups among the different management strategies. The nitrogen bacterial groups were most abundant in the enclosed fertilized grassland and enclosed sown grassland, less abundant in enclosed grassland, and least abundant in the unfenced grassland. The amounts of ammonium nitrogen and nitrate nitrogen decreased with increasing soil depth in all treatments, and were significantly higher in enclosed fertilized grassland and enclosed sown grassland (P<0.05) than in enclosed grassland and unfenced grassland. These results show that, in the alpine meadow, the number and types of soil microorganisms and the contents of different forms of nitrogen can be increased by enclosure with sowing and enclosure with fertilization.