The invention discloses a novel steering detecting device for a lower vehicle of a self-propelled operating platform. The novel steering detecting device comprises a steering detecting device (1), a vehicle bridge full stretching detecting device (2), steering knuckles (3), stretchable vehicle bridges (4) and a lower vehicle body (5). The novel steering detecting device for the lower vehicle of the self-propelled operating platform is used for achieving steering detecting of the aerial working platform with the vehicle bridges being out of line and landing legs being stretchable. Detecting of steering corners of steering wheels is achieved, the degrees of the steering corners of the steering wheels are fed back in real-time, installation is convenient, and the effect is good.