The invention provides a mask plate and a manufacturing method thereof. The mask plate comprises a mask plate frame; the mask plate frame is quadrangular; and aligning round holes are formed in four corners of the mask plate frame. According to the mask plate, the aligning round holes are formed in four corners, with the minimum deformations, of the mask plate frame, so that the position deviationof a coordinate system built by the four aligning round holes in the mask plate manufacturing process is lower, the position accuracy of such structures as shielding bars and support bars welded based on the coordinate system is higher, the manufacturing precision and the yield of the mask plate are improved, and the manufacturing precision and the yield of an array substrate subsequently manufactured by evaporation of the mask plate are higher.