Being recognized by the Kyoto Protocol, soil carbon sequestration and greenhouse gas mitigation in croplands have drawn broad attention. Previous studies showed that soil carbon sequestration measures might have considerable carbon sequestration potentials in the major agricultural countries and the whole world. However, the implementation of the soil carbon sequestration measures could affect the CO2 emission from the fossil fuel use and inputs in agriculture, and influence the non\|CO2 greenhouse gas emissions from the croplands. As the changes of the GHG emissions from outside the soil carbon pool can partly or even fully counteract the mitigation benefit of soil carbon sequestration, such changes are regarded as GHG leakage of soil carbon sequestration measures in croplands. As a result, the net mitigation potential, which concerns both soil carbon sequestration and leakage, turns to be the foremost criteria of the feasibility of a carbon sequestration measure. This paper reviewed several reputable farming practices (e.g., synthetic nitrogen fertilizer application, no\|tillage and conservation tillage, irrigation, straw return, manuring and sewage sludge application) for net mitigation based on their soil carbon sequestration and impacts on the GHG leakage. The results indicated that GHG leakage could offset -241%-660% of the soil carbon sequestration of the above\|mentioned measures. This review suggests more attention be paid to the influences of soil carbon saturation, climate change and land use change on GHG leakages and net mitigation potentials of soil carbon sequestration measures in croplands.