Delineating the basic ecological flow of a river is crucial in ensuring its basic ecological water demand and increasing the amount of water available outside the river. Four ecological flow calculation methods, namely the Tennant method, Qp method, frequency curve method, and mean flow of the driest month method, were selected based on different hydrological periods. By combining them with a long series of hydrological data（1958 to 2020）of the Taiping River in Longnan city, the values taken bydifferent methods were calculated. By analyzing the rationality of the intrayear and inter-annual guarantee rates and considering the fundamental aquatic habitat requirements of aquatic organisms, the results of the frequency curve method were adopted. The basic ecological flow of the Taiping River was determined to be 7.16 m3/s during the flood period and 3.15 m3/s during the dry period. These results can serve as the upper limit of water withdrawal outside the river, promoting the optimal allocation of regional water resources,rationalization of water demand, and providing scientific guidance for “the determination of the water resources based on the four factors” in water-rich areas.