Abstract: Climate change is an increasing global challenge. Greenhouse gas emission via anthropogenic processes is the main cause of global warming. CO₂, CH₄ and N₂O are the main greenhouse gases, accounting for ≈80% of greenhouse effect. It is estimated that each year, 5%~20% of CO₂, 15%~30% of CH₄ and 80%~90% of N₂O in air are emitted from soils. Agricultural soils are the main sources of greenhouse gas emission. This work expatiated the mechanisms and affecting factors of greenhouse gas formation, emission and absorption in agricultural soils. And the contribution of farmland ecosystem to greenhouse effects was discussed. It was indicated that anthropogenic factors such as land use and agricultural activity influenced greenhouse gas formation, emission and absorption in agricultural soils. Because anthropogenic processes affected agricultural ecosystems, greenhouse gas emission reductions for stabilized carbon and nitrogen were possible through improved agricultural cultivation and production systems. This study summarized the latest research advances in source/sink intensities of greenhouse gas emissions from farmlands and how that contributes to greenhouse effect. The study suggested that accurate estimation of source/sink intensities of greenhouse gases and appropriate assessments of greenhouse gas effects were the theoretical basis for reducing greenhouse gas emissions and uncertainties in predicting climate change.