The present invention discloses a heating source, applied in an evaporator of organic light emitting diode to heat a heating container in the evaporator, wherein the heating source comprises a heating coil and a protective component, and the protective component is insulation material, and two ends of the heating coil are connected to a power source to receive voltages to generate heat, and the protective component is located on the heating coil to restrict a deformation range of the heating coil for restricting contact of two adjacent heater strips in the heating coil and preventing the short circuit the two adjacent heater strips. Therefore, the present invention reduces the possibility of the heating coil short circuit and raises the stability of the heating coil, and thus, the stability of the evaporator applied with the heating coil can be provided.