A circular fluidizing bed combustion system with uniform airflow distributing device is provided. The system comprises a fluidizing bed and a uniform airflow distributing device. The fluidizing bed is comprised of a fluidizing bed boiler body, an airflow distributing plate and a plurality of air caps, wherein, the airflow distributing plate is provided inside the fluidizing bed boiler body and divides the inner space of the fluidizing bed boiler body into a fluidizing chamber which is located in the upper portion of the boiler body and an air chamber which is located in the lower portion of the boiler body, and the plurality of air caps are arranged on the airflow distributing plate for injecting the fluidizing air into the fluidizing chamber. The inner space of the air chamber is divided into a distributing chamber that is located under the airflow distributing plate and an air inlet chamber that is located on one side of the distributing chamber by means of a perforated plate. The distributing chamber is comprised of a front wall, two side walls, a top wall that extends upwards obliquely from the upside of the front wall, and a bottom wall extends downwards obliquely from the downside of the front wall. A first guide plate, a second guide plate and a third guide plate are installed in the distributing chamber. This system makes the flow of the fluidizing air entered into the fluidizing chamber through each air cap uniform, and enhances the combusting efficiency of the coal powder in the fluidizing chamber.