Abstract: The effects of slow- release fertilizer amount on photosynthesis, biomass accumulation and distribution, and yield trait are investigated in order to provide references for summer millet cultivation with high productivity.‘Baogu 21’was used as the material in this experiment. At the seedling stage, elongating stage, heading stage, filling stage and mature stage, the conventional assay method was used to analyze photosynthetic rate (Pn), chlorophyll content (Chl), leaf-area index (LAI), dry matter weight of population, dry matter accumulation and transport characteristics of vegetative organs at the late growth stage, the contents of nitrogen phosphorus potassium at mature stage and the accumulation amount of nitrogen phosphorus potassium per unit area, plant characters, yield and harvest indexes. The results showed that among the three treatments covering fertilizer amounts of 0 kg/hm2 (T1), 225 kg/hm2 (T2) and 450 kg/hm2 (T3), Pn and Chl was elevated along with the increase of fertilizer amount at every growth stage. Likewise, LAI and population biomass of plants were also enhanced with the increasing fertilizer application. The biomass of leaves, sheaths, and stems were all increased at spiking and maturity stages along with the increase of fertilizer application, the export biomass amounts increased at the high fertilizer amount. But the differences of transportation efficiencies in vegetative organs were not obvious. At high fertilizer amount, the contents of nitrogen, phosphorus, and potassium in plants were increased, the accumulative amounts of nutrients were significantly elevated, the spike characters were improved, and the yield was increased significantly. The suitable supply amount of slowrelease fertilizer can effectively promote plant growth and development as well as the yield formation capacity, which are closely associated with the increased nutrients absorption, thus to improve photosynthesis capacity of the plants.