A field study was conducted to investigate effects of leguminous green manure and chemical fertilizer N on nitrous oxide (N₂O) emissions from paddy soils under double-crop rice systems. Results demonstrated that during the early rice growing season, the treatment that received both green manure and synthesized N fertilizer emitted significantly more N₂O than the other three treatments did, which received only green manure (V0), only synthesized N fertilizer (FN), or neither green manure nor chemical N fertilizer (F0), separately. The seasonal accumulative N₂O-N emission was 2.75 kg hm^-2 with the former, and 0.29 kg hm^-2, 0.35 kg hm^-2 and 0.18 kg hm^-2, respectively with the other three. During the late rice growing season, 0.34, 0.26, 0.28 and 0.23 kg hm^-2 was emitted from those four treatments respectively, all much lower than that from Treatment VN during the early rice growing season. Besides its effect on N₂O emission rate, the incorporation of green manure also affected N₂O emission time pattern. In Treatment VN, N₂O evolution was concentrated mainly after the midsummer drainage during the early rice growing season, while in the other three treatment the N₂O emission was distributed evenly throughout the entire rice growing season. The results also indicated that there existed great interaction between green manure and chemical N fertilizer during the early rice growing season.