The invention provides a vertical crack grouting and reinforcing method of a prestressed concrete hollow slab bridge bottom plate. According to the method, pressure grouting equipment is mainly adopted to pour a cement-based grouting material into a prestressed concrete hollow plate cavity with a certain thickness, wide, deep and long vertical cracks on the bottom plate can be actively sealed fundamentally through effective adhesion of the grouting material and bottom plate concrete, thereby preventing leakage water inside plates and steams, as well as steam and harmful media and the like in air from entering the cracks to result in rust corrosion and breakage of prestressed steel stranded wires, and further improving the durability and safety of a bridge structure.