The invention provides a single vector hydrophone based measurement method for acoustic reflection coefficient of a large-sample underwater acoustic material. The method mainly comprises the followingsteps: (1) eliminating diffraction sound at the edge of a sample; (2) constructing a signal processing model; (3) separating direct sound from reflected sound; (4) obtaining the acoustic reflection coefficient. On the one hand, broadband narrow pulse is adopted as a form of a transmission signal, time-frequency characteristics of the signal are easy to control, the diffraction sound at the edge of the sample can be separated in time, and the influence of the diffraction sound can be avoided; on the other hand, a single vector hydrophone is regarded as a three-element receiving array, and an array signal processing algorithm of subspace decomposition is adopted for processing measurement data, data processing is convenient and fast, and better real-time property is achieved; besides, a conventional sound source and a vector hydrophone are used as core components of measurement, a traditional large-scale transmitting and receiving matrix is not needed, a huge and complicated measurementsystem is saved, few test steps are taken, and the acoustic reflection coefficient of a concerned frequency band can be obtained by one transmission, so that measurement efficiency is effectively improved.