This article take the C3 plant wheat as an example, through a series of experiments, the summary analysis CO2 density influence the first part was the CO2 density elevates to the wheat to the wheat biomass and the grain output influence, confirmed through the empirical datum, the CO2 density elevated is advantageous to the wheat biomass accumulation and the grain output enhancement. the second part is the CO2 density elevates to the wheat leaf blade membrane fat peroxidation influence, increases the carbon dioxide density to increase to the wheat conductivity and the MAD density influence, the co2 density elevates causes the exosmosis conductivity to reduce, the MDA content increases, the MDA content's change tendency and the exosmosis conductivity are the same. the third part is the CO2 density elevates to the wheat leaf blade active oxygen influence, increases the carbon dioxide density to carry on the experiment once more, the observation wheat H2O2 content and the ultra oxygen anoin free radical influence, obtains the result is the highly concentrated carbon dioxide may reduce in the wheat leaf blade the active oxygen content, can thus reduce H2O2 the toxic action. the last part is the CO2 density elevates to the wheat leaf blade oxidation resistance system's influence, in here through the resistance oxydases' influence, obtains the highly concentrated carbon dioxide has the enhancement regarding the wheat leaf blade SOD vigor and CAT and POD activeness; But to crazy oxide compound influence, also obtains ASA and the Car content increases in the different time, achieves the remarkable level, but along with the birth time's passage, ASA and the Car content drops.