The invention relates to a pneumatic brake pedal device. The pneumatic brake pedal device aims at solving the problem that an existing pneumatic brake pedal device cannot output a brake signal. The pneumatic brake pedal device comprises a base, an air valve assembly and a pedal, wherein the air valve assembly is located on the lower portion of the base and fixedly arranged on the base; the pedal is located on the base and hinged to the base through a hinge shaft; a cam pin shaft is arranged on the pedal and makes contact with an ejector pin of the air valve assembly; the pneumatic brake pedal device is characterized by further comprising an angular transducer. The hinge shaft is in rotation connection with the pedal synchronously, one side of the base is fixedly provided with an installation base, a stator shell of the angular transducer is fixedly connected with the installation base, and a rotary shaft of the angular transducer is fixedly connected with the hinge shaft. According to the pneumatic brake pedal device, when the pedal is trodden for braking, the angular transducer outputs a pedal angle electric signal for controlling the exhaust braking function of an engine. Meanwhile, after the braking strength reaches a certain degree, a driving system clutch is opened, power shutoff is achieved, accordingly, the damage to the engine and a braking system is reduced, the fuel consumption is reduced and the braking capacity is enhanced.