Bird diversity was surveyed by fixed transect lines in Inner Mongolia Saihanwula Nature Reserve in three winters from 2006 to 2009.Total of 51 species belong to 18 families, 6 orders have been recorded, of them 37 are resident birds, 9 winter migrant, and 5 wandering birds. In the survey, we recoded 6 summer migrant birds that wintered in the study area. Of the birds, Aquila chrysaetos is national protected as the first category species, 13 more species are protected as secondary category species, 29 are listed as the species benefic, important, and valuable to people. The habitat of mountain forest had the highest species richness with 37 bird species. The zoogeographical distribution patterns of the wintering birds were divided into 9 types, the high species composition of avifauna resulted from the complex vegetation at the reserve which locates in the zoogeographical transitional regions of the Mongolia-Xinjiang and the Northeast. The winter bird species diversity is relative rich in the study area compared to the surrounding areas.