The design and preparation of hollow non-spherical microparticles are of great significance for their potential applications, but the development of a facile synthetic method based on the one-step production remains a great challenge. In this study, a new template-free method based on the dispersion polymerization was successfully developed to produce hollow polystyrene (PS) microparticles with anisotropic nanostructures in a single step. In the synthesis, ammonium persulfate (APS) which served as an initiator and as a co-stabilizer in dispersion polymerization played a critical role for formation and growth of the highly uniform and stable hollow PS microparticles. The experimental conditions such as the concentration of an initiator and a stabilizer could be adjusted to permit the shape-controlled synthesis of PS microparticles, that is, with control over the particle size and the degree of concavity. Based on our results and observations, a plausible mechanism for the formation of the hollow PS microparticles with novel morphology was proposed.