The invention discloses a waterproof building paint. The waterproof building paint comprises the following components in weight percentage: 15-20 percent of composite fiber, 40-50 percent of asphalt base material or acrylic acid waterproof special latex, 10-20 percent of bentonite, 5-10 percent of talcum powder, water, a softening agent, a dispersing agent, a stabilizing agent and a reinforcing agent, with the total content of the compounds of 100 percent. The waterproof building paint is prepared according to the following steps of: (1) processing the composite fiber into a required length, adding the softening agent to soften the composite fiber first and then adding water and the dispersing agent, and uniformly stirring to form a paste for use; and (2) heating the asphalt base material or the acrylic acid waterproof special latex to 150-200 DEG C, heating the paste prepared in the step (1) to 90-100 DEG C first and then adding the heated paste into the asphalt base material or the acrylic acid waterproof special latex, uniformly stirring, and finally, adding the bentonite, the talcum powder, the stabilizing agent and the reinforcing agent, further uniformly stirring and packaging for delivery.