A construction method of a prefabricated reinforced concrete block prefabricated bridge pier is characterized in that a transverse block (1) with an inverted T-shaped through groove (3) in the upper side is poured, edge ribs (4) are formed on the two sides of the inverted T-shaped through groove (3), the shape of the lower side of the transverse block (1) is symmetric to a transverse shaft, and the transverse block (1) is provided with a round through hole (2); a longitudinal block (5) with a through groove (7) in one side to form an edge rib (9) is poured, and the longitudinal block (5) is provided with round through holes (6); the through groove (7) and the through groove (3) are identical in shape and size, the edge ribs (4) and the edge rib (9) are identical in shape and size, and a combined body, attached to the two back adjacent edge ribs (4), of the transverse block (1) is identical to the through groove (7) of the longitudinal block (5) in size; a plurality of plain round bars (8) are prefabricated; a foundation pit is built; one end of each plain round bar (8) is vertically preburied in the foundation pit; and the plain round bars (8) penetrate from the round through holes (6) and splice the transverse block (1) and the longitudinal block (5), and accordingly the bridge pier can be formed.