Abstract: Tennant method is widely used in the calculation of ecological basic flow, but it has limitations. Jiulong River, Jinjiang River, Mulan Stream and Dongxi Stream in southeast coastal areas of Fujian Province were selected as examples to study the applicability of the Tennant method in this area. The results showed that the ecological base flows calculated by the Tennant method were smaller than the minimum monthly average flow of the rivers, indicating that the Tennant method is not suitable for calculating runoff with large annual and inter-annual variations. Taking the Beixi of Jiulong River as an example for further analysis, the riverbed in the lower reaches of the river has a smaller riverbed slope and larger water passing area. The relationships between cross-sectional flow velocity, the water depth of the main channel, the water surface width and the percentage of annual average flow were relatively flat, which was not possible to regard 10% of the average annual flow as a key or lower limit for river health. Tennant method, calculating ecological base flow with the combination of multi-year average flow and percentage, is not applicable for rivers in the southeast coast of China.