The invention discloses a laser cutting machine cross beam of a roller transmission system. The laser cutting machine cross beam comprises a motor, a slide carriage, an upper roller set, an integratedguide rail rack, an aluminum profile cross beam, a driving gear, a guide rail, a lower roller set, a speed reducer, a sliding table, a laser head, a bearing flat roller and a mounting hole. Accordingto the invention, a cast aluminum profile is used as a main body, so that the weight is lighter, the rigidity is good, and the process is simple; the roller sets and the guide rail rack are integrally matched and are connected with a laser head to complete the movement, with the arrangement of the integrated rack guide rail, the complex alignment work between the guide rail and the rack during mounting is saved, and the precision requirement of the mounting reference is reduced; a roller guide rail system is composed of the roller bearings and is lower in noise, when the roller guide rail isassembled, the concentric rollers and the adjusting rollers are used in cooperation, the pre-tightening between the rollers and the guide rails can be adjusted at any time by adjusting the eccentric distances of the rollers, and the worn guide rails or rollers can be independently replaced without replacing all the guide rails or rollers.