A non-contact type constant distant operated temperature detecting device includes an emitting unit, a detecting unit and a single chip microprocessor. The emitting unit emits a signal to a temperature measuring body. The detecting unit receiving a reflecting signal reflected from the temperature measuring body. The single chip microprocessor is electrically connected to the emitting unit and the detecting unit. The single chip microprocessor determines a measuring distant between the device and the temperature measuring body according to the reflecting signal and when the measuring distance is located in a predetermined measuring range, the single chip microprocessor sent out an enabling signal of measuring temperature.
