A field experiment was carried out in a paddy field under rice-wheat rotation, to study effects of biochar amended at the rice or wheat season on paddy CH₄ and N₂O emissions throughout the cycle of rotation, their consequential global warming potential (GWP) and greenhouse gas intensity (GHGI), with a view to providing some scientific basis for extrapolation of the use biochar in mitigating global warming potentials and in agricultural production as well. The field experiment was designed to last an entire cycle of crop rotation, that is, two cropping seasons, rice season and wheat season, and to have eight treatments in triplicate, i.e. Treatment RB₀-N₀ or CK (zero N fertilizer applied & zero biochar amended in the rice season), Treatment RB₀-N₁ (250 kg hm^-2 N fertilizer applied & zero biochar amended in the rice season), Treatment RB₁-N₁ (250 kg hm^-2 N fertilizer applied & 20 t hm^-2 biochar amended in the rice season), Treatment RB2-N1 (250 kg hm^-2 N fertilizer applied & 40 t hm-2 biochar amendment at rice season), Treatment WB₀-N₀ (zero N fertilizer applied & zero biochar amended in the wheat season), Treatment WB₀-N₁ (250 kg hm^-2 N fertilizer applied & biochar amended in the wheat season), Treatment WB₁-N₁ (250 kg hm^-2N fertilizer applied & 20 t hm^-2 biochar amended in the wheat season), and Treatment WB₂-N₁ (250 kg hm^-2 N fertilizer applied & 40 t hm^-2 biochar amended in the wheat season). Biochar was amended before rice transplanting on June 10, 2012 and wheat seeding on November 10, 2012. CH₄ and N₂O gas emission fluxes were monitored with the static chamber and gas chromatography method. Results show that Relative to Treatment RB₀-N₁ Treatment RB₁-N₁ did not have much significant effect on N₂O and CH₄ emissions, GWP and GHGI, while Treatment RB₂-N₁ significantly improved crop yield by 17.2%, and significantly reduced total CH₄ emissions and GWP by 8.6% and 9.3%, respectively. Treatment WB₁-N₁ did not have much effect on GHGI and GWP, but did increase wheat yield by 21.6%, which in turn significantly reduced GHGI by 21.7%. Treatment WB₂-N₁ significantly reduced N₂O and CH₄emissions by 20.9% and 11.3%, respectively and GWP and GHGI by 15.7% and 23.5%, respectively. In terms of total GWP on a 100-year horizon, the treatments followed an order of RB₀-N₁ > RB₁-N₁ > WB₀-N₁ > WB₁-N₁ > RB₂-N₁ > WB₂-N₁ > RB₀-N₀ > RB₀-N₀, while in terms of GWPs per unit crop grain yield, they followed another, i.e. RB₀-N₁ > WB₀-N₁ > RB₁-N₁ > RB₂-N₁ > RB₀-N₀ > WB₁-N₁ > WB₀-N₀ > WB₂-N₁. Obviously biochar application is more effective in the wheat season than in the rice season, in reducing N₂O and CH₄ emissions, lowering the GWP and GHGI and increasing crop yield of the rotation system. Although Treatment WB₂N₁ was lower than Treatment WB₁N₁ in N₂O and CH₄ emission, and also in wheat yield which to use depends on balance between GHG mitigation and grain yield. However, consequential effects and underlying mechanisms of the use of biochar in the field on scale need further field study Results incorporation at rice season had no significant difference on N₂O and CH₄emissions, GWP and GHGI. Relative to the RB₀-N₁ treatment, the RB₂-N₁treatment significantly improved crop yield by 17.2%, significantly reduced the total CH₄ emissions and GWP by 8.6% and 9.3%, respectively. The crop yield of biochar incorporation at wheat season with 20 t h^-2 significantly improved by 21.6%, and significantly reduced 21.7% GHGI compare with WB₀-N₁. Biochar incorporation at wheat season with 40 t h^-2 significantly reduced N₂O and CH₄ CH₄missions by 20.9% and 11.3%, respectively, significantly reduced GWP and GHGI by 15.7% and 23.5%, respectively. Biochar application at wheat season was better than rice season. iochar incorporation at wheat season on improved crop production, reduced N₂O and CH₄ emissions, while simultaneously lower the GWP and GHGI were superior to the biochar incorporation at rice season in the rice-wheat rotation system.