The invention provides a nesting pedal device for a subway platform and a working method. The nesting pedal device comprises a nesting pedal, a linear driving mechanism and a control device. The nesting pedal comprises a first pedal and a second pedal in nested connection in the first pedal. The first pedal is fixedly installed on the side wall of the subway platform and is perpendicular to a subway platform shielded gate, and a gap is filled partially. The linear driving mechanism comprises a fixed part and a movable part which is fixed to the second pedal. The control device is arranged to respond to a shielded gate opening signal sent by a subway platform control system, and the linear driving mechanism is driven to make the second pedal move out of a first pedal cavity from a first opening. Through the nesting pedal device provided by the invention, when a train reaches a station and the subway platform shielded gate is opened, the nesting pedal stretches out synchronously and automatically, and the gap is filled. When the nesting pedal device goes wrong and cannot be taken back, the train exerts force on a chamfer, thus the second pedal slightly retracts into the first pedal cavity, and passing of the train is not influenced.