We present in this paper a high-resolution projection micro stereo lithography (PμSL) process by using a spatial light modulator as the dynamic mask. This unique technology provides a parallel fabrication of highly complex 3D microstructures for MEMS. Based on the understanding of underlying mechanism, the process model has been developed and verified by experiment. The UV doping effect has been examined as it can effectively reduce the curing depth without compromising the chemical property of the resin. Finally, the fabrication of complex 3D microstructures, such as matrix, micro-spring array, with the smallest feature of 10 μm has been reported.