Two liner drive systems using roller gear mechanism(RGM) are considered in this paper, one is the RPP(roller rack pinion) system that consists of a roller rack and a cam pinion, the other is the CRP(cam rack pinion) system that consists of a cam rack and a roller pinion. This paper presents the finite element study on the contact stresses analyses of a pair of mating RRP and CRP systems during rotation. The result shows that contact stresses obtained from FE analysis are good agreements within 10% deviation with those of theoretical approaches.