This paper presents the design and optimization of a symmetrical compliant XYZ parallel stage for micro-/nanopositioning, which is driven by three piezoelectric actuators (PEAs). A compact design is devised by introducing serialparallel 3-DOF decoupling unit and spatial compound bridgetype amplifiers. Structural parameter optimization has been conducted via finite-element analysis (FEA)-based multi-objective genetic algorithm, which produces a compact physical size of the XYZ stage. The performance of the optimized XYZ stage under different loads are evaluated by FEA simulation study. Under free-load condition, the stage is able to provide a workspace of 143.10×143.12×135.18 μm3. The maximum horizontal cross-axis error is only 0.01%, while the vertical cross-axis error is 5.54%, which is caused by the gravity effect. The loading test result reveals that the maximum bearable load of the stage is up to 74.46 N, i.e., 7.6 kg.