As the greenhouse gas has been increasing continually in recent years, the studies on effects of elevated CO2 concentration on plants have already obtained some results, while the effects of plant photosynthesis on physiological and biochemical level should be investigated further. The main photo-physiological characteristics of urban forest species Ginkgo biloba L. in Shenyang were analyzed in open-top chambers under elevated CO2 concentration in two consecutive growth seasons. The results indicated that in the first growth season the leaf net photosynthetic rates(P<0.01), Hill′s reaction activity(P<0.01), Ca2+/Mg2+-ATPase activity(P<0.05 or P<0.01) and starch contents(P<0.01)all increased under elevated CO2 concentration((700±20)μmol·mol-1)compared with the control. In the second growth season the leaf net photosynthetic rates(P<0.05)and starch contents(P<0.01)both increased compared with the control, Hill′s reaction activity(P<0.01)increased on the 60th day of exposure, Ca2+/Mg2+-ATPase activity(P<0.05)decreased on 30th day of exposure. Compared with the first season, the leaf net photosynthetic rates, Hill′s reaction activity, Ca2+/Mg2+-ATPase activity, starch contents all decreased under elevated CO2 concentration,but chlorophyll contents increased. There was photosynthetic acclimation to elevated CO2 concentration under two consecutive growth seasons in this experimentation.