The invention discloses a pier top block of a precast beam constructed by a stub matching method. The pier top block comprises a top plate, two base beams and three web plates, wherein preformed holes for secondary casting are formed in the top plate; the bottom beams are symmetrically arranged on two sides of an axle wire of the pier top block in the direction of a horizontal bridge; the three web plates are used for connecting the top plate and the two bottom beams; the outer side boundaries, in the direction of the horizontal bridge, of the bottom beams, and the outer side boundaries, in the direction of a vertical bridge, of the web plates, are in the same plane; separation plates are arranged among the bottom beams, the web plates and the top plate in the direction of the horizontal bridge; the side boundaries of the preformed holes in the direction of the horizontal bridge are aligned with the inner side boundaries of the separation plates in the direction of the vertical bridge, and the side boundaries of the preformed holes in the direction of the vertical bridge are aligned with the inner side boundaries of the web plates in the direction of the vertical bridge. The pier top block disclosed by the invention has the characteristics of being convenient to precast, good in construction operability, safe, reliable and good in application prospect.