Mounting method of decorative beam

The invention discloses a mounting method of a decorative beam. The decorative beam comprises a bottom plate, two side plates and a face plate, wherein the side plates are symmetrically mounted on both sides of the bottom plate, and the face plate is mounted between the two side plates; the bottom plate comprises a fixing plate and first clamping grooves symmetrically formed in the two sides of the fixing plate; the face plate and the bottom plate are symmetrically mounted; the face plate comprises a decorative face plate B and second clamping grooves symmetrically formed in the two sides of the decorative face plate B; each side plate comprises a decorative face plate A, a first clamping strip and a second clamping strip, wherein the first clamping strips and the second clamping strips are arranged on the inner side faces of the decorative face plates A; and the first clamping strips are matched with the first clamping grooves in the bottom plate, and the second clamping strips are matched with the second cl