Abstract: A new broadband measurement facility for acoustic characteristics of underwater acoustic materials in free fields is described in this paper. The complex sound pressure reflection coefficients (echo reduction), complex transmission coefficients (insertion loss) and absorption coefficients can be measured for large area samples in an open anechoic tank. Moreover, it is a test (or calibration) standard system to investigate and assess the properties of underwater acoustic material devise in the sonar underwater acoustic system and submarine sound stealth engineering. The broadband compressed pulse superimposition method and the broadband directional sound source are applied in the facility. The lowest measurement frequency is i kHz for the typical large area samples with the size of 1.6 m~ 1.8 m. Utilizing the steel standard sample, the measurement results and theoretical values of acoustic properties have been compared, it shows that this facility can be provided with good precision and reliable measurement data.