Abstract: 【Objective】 By integrated analyzing field experimental results about CH4 and N2O emissions from rice field in China, the authors estimated the mitigation potential of various factors controlling CH4 and N2O emissions in order to provide some suggestions for reducing them in paddy field. 【Method】 A database of CH4 and N2O emissions from rice field in China was constructed in order to study the characteristics of two greenhouse gas emissions and analyze the factors which have a significant effect on them. 【Result】 There clearly existed a zonal distribution law of CH4 emission in China, which showed that the CH4 emissions from Southwest of China were far more than other rice planting areas. It was considered that the factors controlling CH4 emission were water management regimes in rice growing period, water status of non-rice growing season, types of organic or synthetic nitrogen fertilizer and levels of chemical nitrogen fertilizer input (P＜0.05). Compared to continuously flooded (F), flooding-midseason drainage-reflooding (F-D-F), flooding-midseason drainage-reflooding-moist intermittent irrigation, but without water logging(F-D-F-M)and alternative flooding and drainage after transplanting, or moister irrigation but without water logging(M)reduced CH4 emission by 45%, 59% and 83%, respectively. Water status of non-rice growing season determined by cropping system also has a significant effect on CH4 emission. The mode of short drainage (SD), long drainage (LD), and two drainage (TD) could reduce CH4 emission by 42%-56% compared to flooded (F). Simulated effect of organic amendments on CH4 emission from rice field was decreased in the order of crop straw + farm manure (S+FM)＞green manure (GM)＞farm manure (FM)＞crop straw (S)＞composted farm manure and biogas digestion (CM). The effect of different types of chemical nitrogen fertilizer on CH4 emission was unclear. The CH4 emission decreased gradually with increasing chemical nitrogen fertilizer rate (N). When N was 0＜N≤150 kg N?hm-2,150＜N＜250 kg N?hm-2 and N≥250 kg N?hm-2,CH4 emission was reduced by 12%, 29% and 65% compared with treatment of non-fertilizer. There did not exist a zonal distribution law for N2O emission. The factors including water management regimes in rice growing period, the non-rice season water status, and total nitrogen fertilizer input were important for N2O emission (P＜0.05). Compared to CF, the N2O emission was increased by 12%, 140% and 478% under F-D-F, F-D-F-M and M. The nitrogen fertilizer-induced N2O emission factors were 0.43% and 0.68% in F-D-F and F-D-F-M, respectively. By analyzing the water status of non-rice growing season, the average N2O emission increased by 40%-110% under SD, LD and TD, compared to F. 【Conclusion】 There was a trade-off relationship between emission of CH4 and N2O from rice field, appeared water management regimes in rice growing period, water status of non-rice growing season, and the amount of synthetic nitrogen fertilizer. Mitigation measurements in rice fields should be taken consideration comprehensively both of CH4 and N2O emissions. Global worming potential of CH4 and N2O emission from rice field could be reduced by optimizing water regime and fertilizer management.

Key words: rice field, CH4, N2O, mitigation measurements