In this paper, the effects of different straw incorporation years (2 and 13 years) and rates (0, 1.6, 3.2 and 4.8 t/hm²) on CH₄ and N₂O emissions from paddy fields, soil organic carbon (SOC) sequestration rate and net global warming potential (Net GWP) were studied. The results show that CH₄ emissions is increased linearly with the increase of straw incorporation rate both in 2 and 13 years, but the average promoting effect of unit straw incorporation amount on CH₄ emissions in 13 years is 3% lower than that in 2 years. For N₂O emissions, no significant difference is found in 2 years, but the emissions is significantly increased by 55%~171% and shows a linear increase with the increase of straw incorporation rate in 13 years. Meanwhile, SOC sequestration rate varies from 0.40 to 0.50 t/(hm²·a) in 13 years without significant difference among the treatments. Therefore, Net GWP shows a linear increase with the increase of straw incorporation rate, which is carbon source in 13 years. The findings suggest that the effect of straw incorporation amount on Net GWP is regulated by the duration, and the increased GWP gradually completely offsets the emission reduction benefit of soil carbon sequestration and then exacerbates global warming. Therefore, the paddy field is an important carbon source after long-term straw incorporation, and it is urgent to optimize straw incorporation technology to further sequester carbon and reduce emissions to achieve sustainable agricultural development.