The utility model discloses a rotating and braking device of a reinforcing steel bar rotating disk. The rotating and braking device comprises a base, a rotating shaft, a rotating disk and an annular guardrail, wherein the rotating shaft penetrates through the base and is driven by an electric motor, the center of the rotating disk is sleeved on the rotating shaft, and the rotating disk and the rotating shaft are in synchronous rotation relative to the base; the annular guardrail is arranged at the outer side of the rotating disk and is fixedly connected with the base, the rotating disk is provided with a circle of the guardrail in the same circle center with the rotating disk, the bottom part of the rotating disk is provided with more than one friction piece penetrating through the base, and the friction pieces are all driven to ascend or descend by a hydraulic cylinder. According to the rotating and braking device of the reinforcing steel bar rotating disk, disclosed by the utility model, the paying-off operation on a reinforcing steel bar is realized as the electric motor is adopted for driving the rotating disk, the labor intensity during a paying-off process of the reinforcing steel bar is greatly reduced, and the paying-off efficiency of the reinforcing steel bar is increased; meanwhile, the rotating disk is enabled to stop rotating by hydraulically driving the friction pieces, the automation of the reinforcing steel bar paying-off operation can be realized, and the labor intensity is further reduced.