The utility model discloses a core indicator. The core indicator comprises a housing, a power source, a light emitting diode, a wire clamp, a switch, an electric bell and a meter pen wire lead, wherein the power source, the light emitting diode, the switch, the wire clamp, the meter pen wire lead and the electric bell are connected in series through a power line, and the power source, the light emitting diode, the switch and the electric bell are disposed in the housing. According to the core indicator, in case that gear cores are consistent, the light emitting diode of the indicator emits light. Besides, the images are visual, the structure is simple, the production cost is low, the size is small and the portability is high.