Huantai County was famous for its crop straw return and high fertilizer input.The experiment was carried out for studying the effect of straw-return and nitrogen application on the CO-2 emission in high-yield-farmland.The results indicated that different straw return and nitrogen application were two important factors to effect the CO-2 emissions of soil.The CO-2 emission of wheat-and-maize-straw-return treatment was higher than all of the other treatments and wheat-straw-return plus high level N fertilizer application showed the same result.