The study on the responses of spring wheat (Triticum aestivum) potted in open-top chamber to elevated CO2 (542.1 +/- 24.8 and 738.8.0 +/- 25.7 microl x L(-1) vs. 382.4 +/- 24.8 microl x L(-1)) and their effects on Sitobion avenae aphid growth, development and reproduction showed that elevated CO2 was advantageous for spring wheat growth. In treatments 550 and 750 microl CO2 x L(-1), the plant height during May 5 approximately June 14 increased by 2.80% approximately 14.92% and 6.30% approximately 17.56%, and leaf area per plant during April 30 approximately June 19 increased by 5.68% approximately 50.52% and 6.14% approximately 83.45%, respectively, compared with CK. The DC50 and DC75 were brought forward about 0.39 and 0.53 d for treatment 550 microl CO2 x L(-1), and 0.90 and 1.02 d for treatment 750 microl CO2 x L(-1), respectively. Moreover, the stem, leaf, ear and above-ground biomass also had some increase under elevated CO2. Compared with CK, a significant increase of ear length (0.56% and 3.20%) and grain number per ear (12.5% and 18%), but a significant decrease of 1000-grain dry weight (2.23% and 6.34%) were observed for treatments 550 and 750 microl CO2 x L(-1), respectively. With increasing CO2, the chemical constituents in ear, such as glucose, disaccharide, amylose and TSCs/nitrogen ratio increased significantly, while fructose, trisaccharide and total nitrogen decreased significantly. CO2 elevation shortened the preoviposition duration and longevity of S. avenae, and increased the number of offspring per female aphid and mean relative growth rate (MRGR). Compared with CK, the MRGR increased 33.26% in treatment 550 microl CO2 x L(-1), and 74.34% in treatment 750 microl CO2 x L(-1). Furthermore, there was a significant correlation between the MAGR of S. avenae and the TSCs/nitrogen ratio of spring wheat ear.