The invention discloses a wallpaper mechanism for building decoration. The wallpaper mechanism comprises a first support rod and a second support rod which are symmetric, wherein both the first support rod and the second support rod adopt a hollow structure, vertical racks are arranged in the first support rod and the second support rod, horizontal pull rods are arranged in the first support rod and the second support rod, a gear matched with the corresponding rack is arranged at one end of each pull rod, the other end of each pull rod penetrates through one side wall of the first support rodor the second support rod, horizontal cross rods are arranged in the first support rod and the second support rod, a first strip-shaped opening matched with each cross rod is formed in the other sidewall of the first support rod or the second support rod, the cross rods penetrate through the first strip-shaped openings, one end of each cross rod is fixedly connected with one side wall of the corresponding rack, and the other ends of the cross rods are fixedly connected with mounting blocks. A wallpaper tube is stably clamped and convenient to replace.