This thesis studies the PC-based position control of air motor. This control system is carried out under Simulink with Real-Time Window Target. This structure enables the execution to switch rapidly between Simulation and Real-Time control. The air drived system contain uncertainties which cause difficulty on sysem modeling and controller design. This thesis identifies by gradient algorithm the pneutronic system as a second order system with dynamic friction. The sliding mode control is used to eliminate the uncertainties. Its performance is compared with propotional control to verify the effectivenss of sliding mode control.