Photosynthetic characteristics of four field-grown Tree Peony‘Hu hong’、Tree Peony‘Rou fu rong’、Tree Peony‘Wu Long peng sheng’and Tree Peony‘Yin hong qiaodui’were studied comparatively with the CIRAS-1 photosynthetic instrument before the flower blossom out in April. The result showed that the changes during the day in net photosynthetic rate (Pn) of four mature tree peony leaves was typical single peak curve, The change trend between Pn with stomatal conductance are very different. The stomatal conductance begin to decrease at 7:00pm. Tree Peony‘Wu long pengsheng' has the lower The light compensation points (LCP) and Llight saturation point (LSP). Corboxylation efficiency(CE) of Tree Peony‘Yin hong qiao dui’was Relatively higher.