Abstract: Typical double cropping paddy field in Hunan Province and a closed continuous airflow method was used to study on dynamic changes of ammonia volatilization in treatments with different nitrogen (N) application amount. The result showed that total amount of ammonia volatilization was increased significantly with increasing of N application amount. N lost in ammonia volatilization of early rice field was account for 39.8% of N application amount, and lost 46.9% in late rice field, the average lost ratio of ammonia volatilization in double cropping paddy fields was 43.7%. The ammonia volatilization fluxes were significant positively correlated withNH+4-N concentration and pH value in surface water of paddy filed respectively. The results indicated that ammonia volatilization is a main approach to lose of N in paddy fields of Hunan Province.