The invention discloses a unit bathroom waterproof base plate molded through casting. The base plate comprises a plate body which consists of an aluminum profile frame and an aluminum core honeycomb. The aluminum profile frame surrounds the aluminum core honeycomb, and there is a gap between the aluminum core honeycomb and the aluminum profile frame. The gap forms a continuous closed groove which is filled with glass fiber reinforced plastic resin. The upper and lower surfaces of the aluminum core honeycomb are cast with glass fiber reinforced plastic resin. The glass fiber reinforced plastic resin filling the groove and the glass fiber reinforced plastic resin poured on the upper and lower surfaces of the aluminum core honeycomb are integrally molded through a glass fiber reinforced plastic resin cast-molding process, a hollow fully-closed saccular glass fiber reinforced plastic resin sleeve is formed after integral molding, and the glass fiber reinforced plastic resin sleeve is closely connected with the aluminum profile frame and the aluminum core honeycomb. There is no need to make a mould in advance for the waterproof base plate. The problem on how to realize mass production without the need for mould opening is solved. The unit bathroom waterproof base plate completely adapts to the variability of civil engineering structure and size, has good water-proof property, is light, and has a long service life.