Lithium-ion batteries (LiBs), as one of the most suitable choices for electric vehicles (EVs), are characterized with high energy density, efficiency, and long cycle life. As the primary concerns of thermal runaway and capacity fading are determined by internal feature changes, operation and degradation mechanisms of LiBs must be fully understood to evaluate the state of health (SOH) and optimize the design of the Battery Management System (BMS). A new method is introduced to enable a simultaneous monitoring the state of charge (SOC) of the cell and evaluate the SOH during operation. In this paper, experiments and investigations were performed to explore the internal features of the pouch cell working under one complete cycle with ultrasonic waves. In the experiment, 200, 400 and 600 kHz were selected as the frequencies of ultrasound excitation. In addition, Different ultrasonic power was also applied. Results show that frequency and power of ultrasound will affect the variation of amplitude of waveforms at the receiver. Among the 3 frequencies chosen, it seems that when the frequency increased, the ultrasound-based characteristics became clearer, which was in correspondence with Biot theory and elastic properties changes inside the battery. And higher ultrasonic power resulted in marked feature, these key findings provide new insights into condition monitoring and estimation on LiBs.