Using 18 indica rice varieties with different panicle weight, the photosynthetic characteristics and assimilate’s accumulation and transformation in heavy panicle type of rice(HPT)were studied. The results showed that the net photosynthetic rate of the flag leaf in HPT after heading was obviously higher than that in medium panicle type(MPT)and light panicle type(LPT). The reason for the high net photosynthetic rate in HPT was the increase of Rubisco activities and chlorophyll content, and keeping high assimilate ability to CO2 under high and low light intensity, high temperature and low CO2 content, and light midday depression and wide adaptability to environmental conditions. The high net photosynthetic rate of HPT might be also the results of its excellent stomatal characteristics and higher total quantity of stomatal opening degrees(stomatal density X stomatal opening degrees). There was a large amount of dry matter production after heading and obvious high assimilate’s transformation to panicle in H Using 18 indica rice varieties with different panicle weight, the photosynthetic characteristics and assimilate’s accumulation and transformation in heavy panicle type of rice (HPT) were studied. The results showed that the net photosynthetic rate of the flag leaf in HPT after heading was obviously higher than that in medium panicle type (MPT) and light panicle type (LPT). The reason for the high net photosynthetic rate in HPT was the increase of Rubisco activities and chlorophyll content, and keeping high assimilate ability to CO2 under high and low light intensity, High temperature and low CO2 content, and light midday depression and wide adaptability to environmental conditions. The high net photosynthetic rate of HPT might be the results of its excellent stomatal characteristics and higher total quantity of stomatal opening degrees (stomatal density X stomatal opening degrees There was a large amount of dry matter production after heading and obvious high assimilate’s transformati on to panicle in H