By using the method of static chamber-gas chromatograph technique, CH4 and N2O emission fluxes from later rice fields in 2009 were studied under the conventional chemical fertilizer (NPK) and conventional chemical fertilizer + rice straw burning (NPK+SB), while CH4 and N2O emission from rice straw burning was calculated by default value. The results showed that CH4 emissions during rice growing season were very similar in both treatments, meanwhile, N2O emission increased by 22.8% than former, but the difference was not significant at 0.05 level. The highest N2O emission occurred in the period of soil saturation moisture after top-dressing both in two treatments. CH4 and N2O emissions from rice straw burning represented 4.27% and 17.31% of total emissions in NPK+SB respectively. The global warming potential per unit rice grain of NPK+SB was 22% more than NPK. Rice straw burning should be avoided judged comprehensively by consideration of economic and environmental effects.