The invention provides a device and method for producing an oxy-hydrogen fuel by decomposing overheat water vapor. The device comprises an ejector nozzle and a gas receiver pipe, wherein the ejector nozzle is used for enabling water vapor which is pressurized to 0.5MPa and heated to 500 DEG C or higher to be ejected through a nozzle; the interior of the gas receiver pipe is divided into three sections, namely a receiving section which is used for receiving the overheat water vapor ejected by the nozzle of the ejector nozzle and a gas inhaled by an air inlet due to a negative pressure effect, a mixing section which is used for mixing the water vapor and the inhaled gas to generate a turbulent motion, and a diffusion section which makes the treated mixed gas flow out; and a material for making the gas receiver pipe has a heat radiation frequency omega which is matched and resonated with the natural frequency omega o of water molecules, and the gas flowing in the gas receiver pipe is setto fulfill the condition that the Reynolds number is more than 4,000 to generate the turbulent motion. According to the device and method disclosed by the invention, by utilizing the principle of decomposing gases through jet flow and infrared resonance, the oxy-hydrogen fuel can be produced massively and efficiently at an easy rate.