A locking plate fast fastening ceiling fan blades is provided where several nicks are formed, and a thru hole is formed communicating with the open side of one of the nicks. A wedge unit is provided in the thru hole of the locking plate. Thus, when a blade is installed on the blade rack, only the blade is set around the pillars of the blade rack, then the locking plate is made to wedge to the pillar of blade rack, and the wedge unit is made to stay close to and pass through the pillar in the nick communicating with the thru hole for fast and exact completion of fixing of the blade onto the blade rack.