The invention relates to a device for supplying or distributing a powdered fuel to a combustion device, and particularly relates to a selective distributor for primary-air powder from a medium-speed coal mill, which is good in coal powder equalizing effect, small in space usage and low in resistance. The selective distributor is arranged on a primary-air pipe at an outlet of the medium-speed coal mill, and comprises a plurality of adjustable baffle plate mechanisms, wherein the plurality of adjustable baffle plate mechanisms are uniformly arrayed along the external circumference of an inlet of the primary-air pipe; each adjustable baffle plate mechanism comprises a baffle plate mounting seat and a baffle plate, which are fixedly arranged on the periphery of an outlet of the primary-air pipe; the baffle plates are rotatably mounted on the baffle plate mounting seats; the plane where each baffle plate is located is perpendicular to the radial direction of the primary-air pipe; and all the baffle plates synchronously rotate to uniformly guide a flow.