Abstract: An in-situ and in-operando internal state detecting system for an energy storage device comprises a first acoustic signal-emitting acoustic signal emission module, an interior-residing optical sensing module, and a first input optical signal-providing signal demodulation module. The optical sensing module receives a second acoustic signal when the first acoustic signal transmits inside the energy storage device, and outputs a first optical signal, which is demodulated and analyzed by the signal demodulation module to obtain acoustic feature information. Optionally, the signal demodulation module also provides a second input optical signal, and the optical sensing module outputs a second optical signal, which is analyzed by the signal demodulation modulation module to obtain optical feature information.