Porous acryl-based (AUD) composites containing hollow glass microspheres (HGMs) and hollow organic microspheres (HOMs), respectively, were prepared by a UV-curing process in order to evaluate the effect of volume fraction and hardness of hollow microspheres in the composites. From tensile properties and dynamic mechanical measurement, the incorporation of HGMs leaded to the mechanical reinforcement with increasing volume fraction of HGMs in the composites. With Einstein and Smallwood equation, the mechanical reinforcement of porous AUD-HGM composites was found to be mainly attributed to the hydrodynamic effect and rigidity of HGMs in the AUD matrix at low volume fraction of HGMs. Effect of frequency on the dynamic mechanical properties of the respective composites was evaluated. Cole-Cole plots were drawn to understand the heterogeneous nature of the composites. Master curves were constructed based on time-temperature superposition principle in order to explain long-term dynamic behavior of the composites.