Abstract: An ambient pressure compensation structure for an ultraviolet difference spectrum gas sensor includes a closed box, an ultraviolet difference spectrum gas sensor, a digital pressure sensor, a thermostatic controller, an industrial control computer, a pressure regulating assembly and a limiting partition; the pressure regulating assembly and the limiting partition are arranged inside the closed box, the pressure regulating assembly comprises a piston, a regulating rod and a driving motor, the left side of the piston is connected with the regulating rod, the front end of the regulating rod penetrates out of the closed box and is connected with the driving motor, and the piston divides the interior of the closed box into a pressure regulating air chamber and a working air chamber. Also disclosed is an ambient pressure compensation method for an ultraviolet difference spectrum gas sensor.