<p>River treatment projects yield significant flood control benefits, which mainly depend on the scale and frequency of floods. However, existing calculation methods for the flood control benefits of river treatment projects fail to comprehensively consider the uncertainty of flood peak and flood frequency. We proposed a quantitative method for calculating the flood control benefits of river treatment projects that takes these two uncertainties into full account. First, we simulated floods with different return periods before the construction of project and calculated the economic losses. The reduction in economic losses after the project treatment was regarded as the flood control benefits, and thus, the peak discharge-flood control benefits curve of the project was obtained. Subsequently, the flood peak sequence was generated randomly through Monte Carlo simulation. This sequence was then substituted into the peak discharge-flood control benefits curve to calculate the average single flood control benefits of the project. The average annual flood frequency was calculated based on the frequency analysis of peak-over-threshold (POT) floods. Based on the average single flood control benefits and the average annual flood frequency, a method for calculating the flood control benefits of river treatment projects was proposed. Taking the Shuangji River treatment project as an example, the average flood control benefits of a single flood were calculated to be 157&#xa0;million RMB, and the average annual flood control benefits of the project were 424&#xa0;million RMB. This method considers the uncertainty of flood peak and flood frequency, making it more in line with the actual situation. It can also serve as a reference for the evaluation of flood control benefits of other water conservancy projects.</p>