Abstract: Ammonia volatilization was monitored to investigate the ammonia loss in alkaline wetlands. In-situ airflow enclosure was used to measure the amount of ammonia volatilization of marsh soils in 5 typical zones [including permanently floodplain (B), 1-year floodplain (O), 5-year floodplain (F), 10-year floodplain (T), 100-year floodplain (H)] which are divided by different flooding frequencies along the vertical direction of the river channel in different floodplain wetlands of the Xianghai National Nature Reserve, Jilin Province, in different growing seasons (July, September, and November 2010). The highest ammonia volatilization rate (1.155 mg/m²) was observed in September (0.651 mg/m²) followed by November, while the lowest rate was in July (0.175 mg/m²). There were significant differences in the amount of ammonia volatilization in different sampling seasons. However, no significant differences were observed in ammonia volatilization rates between sites in July. The values of ammonia volatilization appeared “U” style with increasing flooding frequencies in September (i.e. the ammonia volatilization rates were higher in those zones near or far away from the river channel than those in the middle zones). However, the ammonia volatilization rates were higher in both the 5-year and 10-year floodplains in November. Grazing was one of the important factors that influenced increased nitrogen losses through ammonia volatilization from alkaline wetland soils.