1. A method for regulating magnetic multi-domain state, comprising: when a current is applied to a magnetic thin film, applying an external magnetic field having a magnetic field strength of 0 to 4×10 5 A/m to regulate magnetization state of the magnetic thin film; wherein the current is configured to drive movements of a magnetic domain of the magnetic multi-domain states in the magnetic thin film, and the external magnetic field is configured to regulate generation of new magnetic domain in the magnetic thin film and state of the magnetic domain during the movement, so that the magnetic thin film is in a stable magnetic multi-domain state.