The invention discloses a building material decoration system comprises an external corner trim, an internal corner trim, a connecting decoration plate, two groups of waist boards, a baseboard and wall decoration plates. The external corner trim is arranged at an external corner of the wall, and the internal corner trim is arranged at an internal corner of the wall; the connecting decoration plate is arranged between the external corner trim and the internal corner trim; the waist boards are arranged on the wall transversely and are assembled in one row correspondingly; the baseboard is arranged on the lower portion of the wall, and the wall decoration plates are arranged on the wall. The building material decoration system is convenient to assemble, force, time and material are saved, decoration is attractive and bright, structure is simple, and the building material decoration system is quite practical.