Abstract: Based on the combination of state matrix and Legendre series method with Biot's theory, a theoretical model for wave propagation in multi-layered porous lithium-ion batteries is established. Taking 1.9 mm-thick soft-pack cobalt oxides lithium-ion battery as an example, the influence of State Of Charge (SOC) on the multi-mode dispersion curves is numerically analyzed. At the same time, a frequency-domain simulation model of the wave propagation characteristics of a multilayer porous lithium-ion battery is established, and the ultrasonic guided wave dispersion curves in frequency-domain simulation are extracted. In addition, based on Macro Fiber Composite (MFC) transducer which possesses small volume and strong flexibility, the influence of different states of charge on the acoustic behavior of lithium-ion batteries is explored experimentally. The cross-correlation analysis is used to obtain the shift in the time of flight during the discharging process. The mapping relationship between acoustic wave behavior and SOC of a 1.9 mm-thick soft-pack cobalt oxides lithium-ion battery is established.