The invention relates to a pin-tooth-transmission arc-shaped spillplate mechanism with a self-locking device. The pin-tooth-transmission arc-shaped spillplate mechanism comprises an arc-shaped spillplate assembly, circular pin teeth, a hydraulic motor, a driving wheel, a brake assembly and a brake wheel, wherein the arc-shaped spillplate assembly can freely rotate around a planetary mechanism and is axially fixed; the hydraulic motor is fixed inside a rocker arm housing hood through a screw group III; the brake assembly is fixed inside the rocker arm housing hood through a screw group IV; the driving wheel is mounted on the hydraulic motor and is meshed with a pin wheel; the brake wheel is mounted on an axle of the brake assembly and is meshed with the pin wheel; the hydraulic motor drives the driving wheel to rotate; the driving wheel drives the pin wheel to rotate and drives the arc-shaped spillplate assembly to adjust the position; at the moment, a brake in the brake assembly is in a releasing state and the brake wheel rotates along with the pin wheel; once the arc-shaped spillplate stops overturning, the brake in the brake assembly breaks and the brake wheel locks the arc-shaped spillplate; the pin teeth start transmission, and coal ash cannot accumulate on the circular pin teeth.