The present disclosure provides a driving substrate, a method for preparing the same, and a flexible display device. The driving substrate includes: a base substrate; a first driving function layer arranged on a first surface of the base substrate, the first driving function layer including a plurality of driving thin film transistors and a plurality of signal wirings, and at least one of the plurality of signal wirings being of a single-layer structure and having a thickness greater than a threshold; a pad layer arranged on a surface of the first driving function layer away from the base substrate, the pad layer including a plurality of first pads and a plurality of second pads, and each first pad being connected to a first electrode of the corresponding driving thin film transistor and each second pad being connected to a common electrode line in the plurality of signal wirings.