Abstract: A method suitable for measuring the insertion loss of underwater acoustic materials in a pool of limited size was proposed,which is called "virtual focusing method".This method uses an arc-shaped emission array to scan the sample with certain rules.By superimposing the received data,the contribution of the samefrequency acoustic interference is randomized,thereby extracting the transmitted wave signal reflecting the acoustic parameters of the materialsIn a 5.5 m × 3.5 m × 3.5 m non anechoic water tank,the measurement frequency is 2~15 kHz and the insertion loss of the samples of 1.1 m × 1 m × 8 mm standard aluminum plate and 1 m × 1 m × 35 mm polyurethane material were measured.The results show that the measurement values were in good agreement with the theoretical values,and the measurement uncertainty is 2.0 dB(k=2).