The invention discloses a finished concrete membrane, a molding mold and molding and mounting methods. The finished concrete membrane comprises a membrane body; the molding mold comprises a molding mold body; the molding mold body is a cavity formed by a bottom mold and a side mold; the molding construction method comprises the steps of: (1) brushing a demolding agent; (2) casting the finished concrete membrane; and (3) molding the finished concrete membrane; and the mounting method comprises the steps of: (S1) preparing construction; (S2) mounting the finished concrete membrane; and (S3) blocking a reserved round hole. The lower part of the membrane body is bracket-shaped, so that the contacted area of the membrane body with the ground is increased, and the stability of the finished concrete membrane after mounting is improved; when the finished concrete membrane is molded, once casting molding construction can be realized, and demolding is convenient; and when the finished concrete membrane is mounted, two adjacent finished concrete membranes are firmly joined, the contacted area of the bottoms with the ground is increased, and the waterproof effect of a waterproof base layer of a molded basement baseplate is excellent.