Methane emission rate was measured in 1993 using an automatic measuring system built by the Institute of Atmospheric Physics, Chinese Academy of Sciences. Methane emission factor is preliminary available for rice fields in South China region, which takes about 20% of the total rice harvesting area in China. Then the methane emission factors are already available in all the five major rice culture regions in China. The seasonal variation of methane emission rate depends mainly on the variation of air temperature and flooding condition. The afternoon peak mode is dominant for diurnal variation. The methane emission rate form this experiment field is rather low, which may mainly due to the unique cultivation system in Guangzhou that rice fields are normally kept free during winter time and in the gap between early and late rice growing season. The low dosage or even without organic manure may be another important reason. In our experiment the water flooding condition was kept normal as in the local region so that the methane emission factor can represent more properly the real emission value from actual rice paddy fields. Annual mean temperature and soil organic matter are not the factors to explain the spatial variation of methane emission rate from rice fields. The seasonal average of methane emission rate was 0.5±0.6 mg/m²•h. According to the available date set for methane emission rate from various rice fields in China, and relevant area of rice cultivation, total methane emission in Chinese rice paddies can be estimated 11.1(10.2~12.8) ×10¹² g/a.