Abstract: To investigate the effects of CO2 capture agent on photosynthetic characteristics, physiological and biochemical indices and yield traits of foxtail millet, the authors used‘Yugu 28’as experimental material and analyzed the indices under different concentrations of CO2 capture agent at flowering stage. In this experiment, 4 treatments were set up: N0 was no spraying of CO2 capture agent (CK), the concentration of N1, N2 and N3 was 2.25, 4.50 and 6.75 L/hm2, respectively. The results showed that photosynthetic characteristics, physiological and biochemical indices and yield traits of millet were significantly higher than those of control under N1, N2 and N3, and all peak values appeared under N2. Under N2, compared with CK, the contents of chlorophyll a, chlorophyll b and chlorophyll (a+b) increased by 41.8%, 53.8% and 48.2%, respectively; the photosynthetic rate, intercellular CO2, stomatal conductance and water use efficiency increased by 30.9% , 76.5% , 66.7% and 38.7% compared with that of CK, respectively; the soluble sugar and soluble protein content increased by 95.1% and 5.4- fold, respectively; the activity of SOD, POD and CAT increased by 26.7%, 86.8% and 90.0%, respectively; while the height of gravitational center decreased by 8.3%, and the bending force and culm lodging resistant index increased by 56.5% and 69.2%, respectively; the spike length, panicle grain mass, thousand grain mass, aboveground biomass and yield increased by 13.7%, 60.4%, 5.3%, 58.1% and 9.2% , respectively. As suggested above, it is of great importance to enhance photosynthesis, improve physiological and biochemical indices and increase yield of millet with applying certain concentrations of CO2 capture agent.