A new joint mechanical and electrical simulation platform of a motion stage (reticle or wafer stage) was introduced of a step-and-scan lithography. In this platform the motion stage control object model represented in the form of a state-space model was extracted from its finite element (FE) model, which was then inserted into the other control models built by Matlab/simulink to form this simulation platform. Because a state-space FE model has not only the stiff-body information but also that of the mechanical structure modals of a motion stage, hence when compared with a stiff-body model or a theoretic one it is much closer to an actual motion stage. A simulation example of a reticle stage control system was given of a step-and-scan lithography, in which the time and frequent performance indices were compared with both a stiff-body model and a state-space one respectively, and it further showed that the state-space model was much more adapted to meet the modeling requirements of an actual motion stage than that of a stiff-body one.