Disclosed is a method of detecting an earphone state relative to an earphone case, one of the earphone and the earphone case provides a first touch sensor, and the other of the earphone and the earphone case provides a second touch sensor and a capacitor electrically connected to the second touch sensor, the method includes: acquiring a capacitance parameter of the first touch sensor, wherein the capacitance parameter comprises a capacitance value or a capacitance change; and determining the earphone state based on the capacitance parameter, where the state comprises: the earphone in the earphone case or the earphone out of the earphone case. An device and an earphone assembly are further disclosed.