A heating device and its temperature control method, wherein an NTC element envelops a core member, a sensing wire is wound around an outside periphery of the NTC element for making parallel connection of the core member with the sensing wire; further, a capacitor, the sensing wire and an electric resistor are connected in series to form an RC circuit, the RC circuit is connected with a microprocessor and a switch. Thereby when the microprocessor outputs a control signal containing at least a duty cycle square wave in a predetermined time to control the switch to make a direct-current electric power source electrically charge/discharge for the RC circuit; meanwhile, the microprocessor measures RC time constant of the RC circuit, and when it detects changing of the RC time constant reaches a preset state, it outputs a control signal to make the heat emitting line and the direct-current electric power source in a state of circuit turning on or off, such that the heat emitting device is kept at a predetermined working temperature.