Abstract: A method using time reversal (TR) technique to measure the insertion loss of passive materials is presented. To measure the insertion loss with this approach, the received signals are firstly focused according to the TR theory when a sample is not placed between the source and the received array. Then, the sample is placed near the received array and the TR processing is again employed to realize the focus of the received signal. Finally, the insertion loss of the sample is evaluated with these focusing signals. Because the TR processing can focus the energy in spatial domain and time domain, the method can be used to measure acoustic properties of passive materials with reflections induced by boundaries or low frequency sources. Two samples with the same size of 1.1 m×1.0m×5 mm are tested in a wave guide tank. The method is demonstrated by the comparison of the theoretical and the experimental results with the measured frequency range of 1-20 kHz.