The influence of earthworm and elevated CO₂ on cotton leaf decomposition and C and N transformation in the soil by the 56 days experiment treated with earthworm under different levels of CO₂ were analyzed. The effect of different levels of CO₂, cotton leaf and their interactions on C content in soil was not significant, while interaction of earthworm and cotton leaf was significant. Earthworm didn′t influence the N content solely, but the combined effect of elevated CO₂ and earthworm could influence the N content. The interaction of CO₂, earthworm and leaf was more significant than that of earthworm and leaf. Our results indicated that the elevated CO₂ made the component of litter decomposition easier and improved the ability of decomposition and transformation of litter through earthworm, resulted in the change of C and N content in soil.