This paper presents the design for performance improvement of 2-axis cartesian coordinate robot. We cannot obtain the expected design performance unless we select the best-fit linear system for the robot. For this, this paper finds conditions of most suitable to select a LM(Linear Motion) guide and design a 2nd axis arm. By simulation results, the 2nd axis LM guide and the 2nd axis arm structure are confirmed that influence to the deflection of work piece end and the loads on 1 axis LM block. On using LM guide that have capacity near, this paper shows that the maximum load on LM block of 1 axis increases 4.23% and the maximum deflection of work piece end increases 7.95%.