Abstract: Consideration of historical flood could improve the accuracy and reliability of flood frequency analysis. In practice, however, some historical floods cannot be quantitated and are difficult to use in a common deterministic methods, thus lowering the reliability of parameter estimation and design flood in the flood frequency analysis. This paper focuses on the coupling of a Bayesian method a maximum likelihood estimator in the frequency analysis using non-quantitative historical floods. This coupling method and its application are demonstrated in a case study of synthetic and measured flood series. Compared to several traditional deterministic method, the coupling method not merely makes it possible to make use of non-quantitative historical floods, but can improve estimation accuracy.