Abstract: Studying the effects of CO₂ concentration and temperature elevation on soil oxidoreductase enzyme activities during different crop periods is helpful to analyze the effects of climate change on soil nutrient cycle processes. This study investigated the response of soil oxidoreductase enzyme activities to CO₂ concentration increase and temperature increase at four millet (Setaria italica) growth stages, including anthesis, 10 d after anthesis, grain filling and maturity stages, respectively, by combining artificial climate chamber and pot control experiments, simulating three climate scenarios (current environmental CO₂ concentration and temperature, only elevated CO₂ concentration, CO₂ concentration and temperature elevation) and two water conditions (adequate water supply and mild drought). The results showed that the increase of CO₂ concentration from 400 to 700 μmol·mol⁻¹ significantly inhibited soil catalase and polyphenol oxidase activities, they were respectively reduced 2.86%-7.99% and 8.63%-27.00%. Temperature increased 4 ℃ significantly promoted soil catalase and polyphenol oxidase activities, they were respectively increased 2.10%-9.83% and 10.03%-24.96%. Interaction between increased CO₂ concentration and warmth had no significant effect on the activity of two soil enzymes during the four growth stages of millet. The growth periods of millet had a significant effect on soil oxidoreductase activities. Moreover, the interaction between increased CO₂ concentration and growth stages had a significant effect on the soil oxidoreductase activities, but it between temperature increase and growth stages only had a significant effect on soil polyphenol oxidase activity. The results of redundant analysis (RDA) showed that soil NH₄⁺ and MBN had high degree of explanation for changes of soil polyphenol oxidase activity. Elevated CO₂ concentration inhibited soil oxidoreductase enzyme activities, while elevated temperature increased soil oxidoreductase activities. The effects of the CO₂ concentration and temperature elevation on soil oxidoreductase activity presented an antagonism in most millet growth stages. Millet growth stages affected the response of soil oxidoreductase enzyme activity to climate change. Soil available N content was an important factor affecting the activity of soil polyphenol oxidase.