Abstract: A gas chromatography method is introduced to determine CH₄ emission flux by using carbon molecule sieve as solid phase. This method is easy, quick and exact, and its air sample needn’t be undertook preliminary steps, such as freezing, drying and dehydrating. By using this method, during the later rice growing period in the experimental field of South China Agriculture University in 1994, the day average CH₄ emission flux was 8.34 mg/（m². h）, which can represent the CH₄ emission flux of rice field in Guangzhou Region.