Abstract: An improved bracing bracket for arched window blinds includes a protrusive seat which has a wedge notch on the top rim to couple with a mating plank so that the coupled protrusive seat and the plank may serve as the installation basis. A left material and a right material may be bonded to two sides of the plank. The protrusive seat has a mark in the center of the front side and the rear side to align with a window sill to bond the bracing bracket to the window sill without skewing to facilitate fast installation.