Abstract: It has been predicted that atmospheric CO₂ enhancement will increase activity of soil enzymes as the result of CO₂-induced carbon entering the soil through plant.To investigate influence of atmospheric CO₂ enhancement on activity of soil enzymes,an experiment was conducted in Yangzhou,Jiangsu,China within the China FACE(free air carbon dioxide enrichment) Project System.Two levels of CO₂ concentration and two N application treatments were designed,and wheat straw was added into soil at the rate of about 3 000 kg·hm^-2 in all treatments.Soil samples were collected at different growth stages for analysis of activity of dehydrogenase,urease,phosphatase and invertase in the soil.Results reveal that atmospheric CO₂ enhancement significantly increased activity of dehydrogenase,urease and invertase in the soils applied with the same N rate,but decreased that of phosphatase.However,regardless of CO₂ concentration,activity of dehydrogenase and urease was higher in low N treatments than in high N treatments,but it was in contrast for phosphatase,whereas the activity of invertase differed slightly between the two treatments.