The invention belongs to the technical field of rice field fertilization, and discloses a synchronous fertilization method under triple cropping production of a red soil rice field. The method comprises the following steps that potato and rice varieties are selected; no-tillage furrow sowing straw in-situ covering or mechanical stubble cleaning, rotary tillage, ridging and sowing film covering after ratoon rice stubble is adopted, the fertilizing amount is reduced, and all straw is returned to the field after potatoes are harvested; seedling tray seedling raising throwing planting is adopted,the seedling throwing planting age does not exceed 25 days, the fertilizer application amount is reduced, and the mature machine harvests broken straw and returns the straw to the field completely; and germination accelerating fertilizer is applied 7-10 days before mechanical harvesting of middle-season rice, the fertilizing amount is reduced, and full-amount in-situ covering and returning or mechanical rotary tillage, turning and pressing returning of straw harvested by a maturation machine is achieved. By utilizing the synchronous fertilization method under triple cropping production of thered soil rice field, the grain yield is obviously increased, the soil fertility of the rice field is obviously improved, the land resource utilization rate is obviously increased, the number of agricultural products is increased, and the grain and oil self-sufficiency guarantee is improved.