From 5 May 2003 to early June 2005, nest site selection of Black-necked Cranes Grus nigricollis was studied at the Ruoergai Wetland Nature Reserve (RWNR), an important breeding area for the species in China. Results showed that the crane nests only in wetland environments, including lake, swamp and river microhabitats. However, the bird showed different selection patterns in these microhabitats. According to the Ivelev selectivity index (S.I.), cranes preferred lakes and avoided swampy areas, while they used river areas in proportion to their availability. Factors associated with the selection of nest sites included water body size, distance to water, water depth and the level of nest concealment. Nest size was a function of the microhabitat used for nesting; nests were largest in lakes, and similarly-sized in swamp and river habitats. A certain water depth was a prerequisite for nest site selection (mean = 31.1 cm), but no differences were found among different microhabitats. Compared with nests found in Qinghai, Tibet, and Ladakh, nests in Ruoergai Wetland were smaller, but water depth near nesting sites was higher (mean = 31.1 cm vs 18.2 cm). Different plant communities, climate and disturbance are likely to be related to these differences. Conservation efforts should focus on the protection of existing lakes, minimizing disturbance impacts and maintaining small patches (i.e. 100 m2 water bodies) of swamp areas as important buffer zones. In the future, restoration of wetlands to decrease fragmentation, and reduction of habitat degradation are advocated for effective conservation of this species.