Direct impact of elevated CO₂ (750 μl/L) on growth, development and reproduction of cotton bollworm Helicoverpa armigera (Hübner) were examined in closed-dynamic CO2 chamber (CDCC-1)under artificial diet between CO₂ treatments. The results show that compared with ambient CO₂ (370 μl / L ), as untreated control, the life-span of H. armigera was delayed under elevated CO2 (15.14%; p<0.01), and H. armigera larvae under elevated CO₂ fed more artificial diet (8.03%; p< 0.01) and produced more frass (14.54%; p<0.05) than those in the ambient CO₂. We also found that elevated CO₂ marginally influenced the artificial diet-utilization efficiency of H. armigera larvae that decreased in relative growth rate (RGR), relative consumption rate (RCR), conversation efficiency (ECD) and approximate digestibility (AD). Our data also indicate that elevated CO₂ influenced nutritional substance contents and activity of some enzymes in H. armigera larvae. For the larve under the 750 μl/L CO₂, their free fatty acid, SOD, TChE and AMS significantly increased, whereas their protein, total amino acid and GSH-PX significant decreased.