A dynamic traffic control method is disclosed that controls traffic in a radio network system where a radio network controller causes plural radio base stations to change radio outputs. The method comprises a step of measuring a channel utilization rate of each of cells of the radio base stations every predetermined period, a step of predicting whether the rate of a first cell of the cells reaches an implementation level, at which radio output control over the first cell is required, in a next period based on a movement of the rate in the past if the channel utilization rate of the first cell is at a warning level, and a step of reducing the radio output of the first cell and increasing the radio output of a second cell adjacent to the first cell if the rate of the first cell is predicted to reach the implementation level.