In this paper a FACE (free air carbon dioxide enrichment) experiment with 4 kinds of soil managements (fallow, 0 organic matter amendment (0res), 50% harvested straw amendment (0.5res) and 150% harvested straw amendment (1.5res)) was conducted to investigate the responses of soil enzyme activities. Results showed that elevated CO2 had no effect on fallow soil. Straw amendment increased the activities of soil dehydrogenase, β-glucosidase, arylsulphatase and FDA hydrolysis. With no straw amendment elevated CO2 concentration increased the activities of soil dehydrogenase, β-glucosidase, arylsulphatase, invertase and FDA hydrolysis by 14.88%, 19.41%, 17.12%, 11.69% and 4.47% respectively. FACE effect increased firstly then disappeared with the increase of straw amendments.