CH_4 and N_2O emissions under three crop rotation systems were measured using static chamber/gas chromatographic techniques to study the anniversary of greenhouse gas emissions and the Global Warming Potential(GWP). The three systems included double-cropping paddy(R-R) (Oryza sativa L.), corn(Zea mays L.)-later rice system(C-R) and early rice-corn system(R-C). The results showed that paddy field cropping pattern took a dominated role in CH_4 emission. The N_2O emission was increased significantly in maize season; The emissions of CH_4 and N_2O were decreased while the former was reduced significantly by 68.5%(P<0.05) compared with the R-C treatment. The anniversary total emission of CH_4 in R-C and C-R treatment were reduced by 53.6%(P<0.01) and 183.9%(P<0.01) but increased by 257.0%(P<0.01) and 245.2%(P<0.01) of N_2O respectively compared with R-R treatment. The order of GWPS under different crop rotation system was in following: R-R(8 855.3 kg CO_2·hm~(-2))>R-C(4 881.4 kg CO_2·hm~(-2))>C-R(2 116.4 kg CO_2·hm~(-2)). Combining the advantages of temperature and light resources in this southern area, the cropping pattern of corn replacing late rice(R-C)is a feasible way to mitigate the greenhouse effect.