Abstract: Birds are important indicative organisms of habitat changes. Through continuous monitoring and analysis of birds in a given area, we can objectively understand the trend of bird species diversity. Inner Mongolia Tumuji National Nature Reserve is well known for conserving the iconic endangered species, such as great bustard (Otis tarda dybowskii)and red-crowned crane (Grus japonensis), as well as the important bird breeding area, stopover site and wintering ground in China. Due to long-term farmland reclamation and overgrazing, the grassland and wetland in this reserve had been degraded, and bird habitats had been suffered from fragmentation, which had influences on the bird population dynamics. However, the inter-annual and monthly variability of bird population dynamics is not yet clear. The aim of this study is to analyze the temporal and spatial changes of bird diversity in Tumuji Nature Reserve, and determine the dynamics of bird populations. By combining line transect and point count surveys, the birds were field monitored and surveyed during the breeding season for five consecutive years on May and June from 2015. Based on the monitoring data, the population dynamics, bird diversity and bird evenness index were analyzed in Tumuji nature reserve for the past 5 years (2015-2019). A total of 99 species of birds were detected belonging to 15 orders and 33 families, of which Anseriformes and Charadriiformes are the dominant species, and the population size of great bustard showed a spatial and temporal change. There were significant spatial differences in the number of bird species and population size. The average bird community diversity was 2.39±0.39 across all surveying sites, with wetland being higher than that in grassland, and farmland-dominated habitat diversity the lowest. The average evenness index was 0.33±0.05, and birds distribution varied among geographical sites. Conservation practice should be directed to the breeding season, and surveying intensity should focus on determining the key protection area, and ensure that the bird breeding is free from human interference. Meanwhile, it will facilitate the protection and monitoring of biodiversity, and provide scientific support for evaluating the effectiveness of protected area management and optimizing protection policies.