In this paper, sliding mode control (SMC) is implemented on an XY parallel micropositioning stage for a sub-micron accuracy tracking control. To design the controller, a dynamics model of the system is established with the combination of the flexure hinge-based stage and piezoelectric actuator (PZT), and model parameters are identified by experiments and finite element analysis performed via ANSYS software package. Moreover, a high-gain velocity observer is adopted to estimate the feedback velocity from the measured position. The efficiency of the designed SMC controller over traditional PID controller is demonstrated through simulations and the variations of design parameters on control performances are examined as well. The results show that the SMC can compensate for unmodeled hysteresis well, which provides a sound base for practical control of the micropositioning stage dedicated to micro/nano scale manipulation.