Abstract: In order to explore the effect of corn straw and its biochar application on N₂O and CH₄ emissions from laterite soil under flooding condition, four treatments with the same amount addition of straw, straw + biochar (Mix), biochar, and control (CK), into laterite soil were designed to investigate the possible formation of strong reductive environment and their impacts on soil methane (CH₄) and nitrous oxide (N₂O) emissions. The results showed that compared with CK, straw and Mix treatments obviously decreased Eh within five days of incubation, while the biochar had an insignificant impact on soil Eh. The straw, biochar and Mix treatments increased soil pH, but there was no significant difference in pH between the straw and biochar treatments. Compared with CK, the other three treatments decreased soil N₂O emissions, but the straw treatment significantly increased soil CH₄ emission only, resulting in a significant increase of global warming potential. In addition, the Mix treatment significantly increased soil pH, soil organic carbon, total nitrogen and potassium. Therefore, the combined application of corn straw and biochar under submerged condition could not only decrease the combined greenhouse effect of CH₄ and N₂O, but also improve soil fertility by affecting the reductive condition of the laterite soil in Hainan, China.