In order to systematically understand the current situation of river ecological base flow in different regions of China, two different compliance assessment methods of monthly average flow and daily average flow were used to evaluate the current situation of the ecological base flow of river cross-sections, and the noncompliance reasons in different regions were preliminarily analyzed based on 90 main river cross-sections with established ecological base flow targets and the flow data in the period from 2009 to 2018. Regulation and guarantee measures were put forward. The results showed that the ecological base flow compliance rate of main river cross-sections in China was 73. 3% when the monthly average flow was taken as the evaluation unit. The rate dropped significantly to only 26. 7% when the daily average flow was taken as the evaluation unit. The compliance rates of ecological base flow in the northeastern and southwestern regions were better than other regions. The Huaihe River system and Yi-Shu-Si River system from the Huang-Huai-Hai Region, and the Xijiang River system from the Southeast coastal region were the three river systems with the worst ecological base flow compliance rates in the evaluation. Human activities, including high total water withdrawal, seasonal conflicts in water withdrawal, and irrational dispatch of water conservancy projects, were the main noncompliance reasons, accounting for 62. 3%.