The invention discloses a prefabricated type sewage plant biochemical pool and an installation method thereof. The biochemical pool comprises L-shaped members, transverse baffle plates and a prefabricated base plate, wherein the L-shaped members comprise integrally formed side baffle plates and bottom plates; at least two L-shaped members are oppositely arranged in a mirroring mode and assembled into a U-shaped groove-shaped structure, the bottom plates are attached to the top surface of the prefabricated base plate and are mounted on the prefabricated base plate, and the two ends of the U-shaped groove-shaped structure in the length direction are plugged with the transverse baffle plates correspondingly. The installation method comprises the following steps of, (1) integrally pouring andmolding the L-shaped members and the transverse baffle plates; (2) transporting the L-shaped members and the transverse baffle plates to the site, and positioning the bottom plates and the prefabricated base plate; (3) sequentially installing the L-shaped members in the transverse direction or the longitudinal direction, and installing the transverse baffle plates after a predetermined size is reached according to the requirements of the pool; and 4) carrying out joint filling treatment on the joint of the L-shaped members and the transverse baffle plates with sealants and water-swellable adhesive tapes. According to the method, the workload of on-site wet operation is reduced, resources are saved, and the construction cost of the pool is lowered.