Abstract: In summer,diurnal changes in photosynthesis and photochemistry efficiency were examined and analyzed in the Ginkgo fieldcultivated in four different habitats of photosynthetically active radiation,which were equivalent to 100%,54%,18% and 11% of nature sunlight respectively.The results were as follows:decline of net photosynthesis rate in midday was lightened or even avoided by means of shading.The mean Pn during all day went down as shading intensity increased and those in 54%,18% and 11% of nature sunlight,for example,were equivalent to 89.8%,66.9% and 41.6% of that in nature sunlight respectively.The mean Fv/Fm,Fv and PSⅡ during all day went up as shading intensity increased and compared with that in nature sunlight,the mean Fv/Fm in 54%,18% and 11% of nature sunlight increased by 6.1%,13.4% and 13.7%,the mean Fv increased by 21.1%,71.1% and 83.3%,and the mean PSⅡ increased by 47.3%,99.3% and 105% respectively.The mean Drate and Prate during all day decreased as shading intensity increased.Compared with the mean Drate in nature sunlight,that in 54%,18% and 11% of nature sunlight were equivalent to 39.3%,7.2%,4.5% and the mean Prate were equivalent to 78.5%,41.6%,27.4%.The results suggested that much more proportion of absorbed light energy was allocated to photochemistry reaction to compensate for insufficient illumination in the habitats lack of light.Contrarily,much more proportion of absorbed light energy was allocated to thermal energy dissipation to protect photosystem from photooxidating or even photodamage in the habitats with more supplies of light.