Microfluidic bead-based microarrays offer an ideal platform for chemical and biological applications, such as bio-molecule detection, diagnostics and drug screening. Despite the numerous advantages inherent to dynamic bead-based microfluidic arrays, current microparticle trapping methods remain limited in terms of trapping density and device resettability. Here we present a simple, resettable microparticle arraying system by utilizing geometric designs in microfluidics to manipulate microscale hydrodynamics. Under forward fluidic flow, arrays of individual 15 µm diameter microbeads immobilize in designated trapping positions between microposts. Under backward fluidic flow, the arrayed microbeads release rapidly to reset the microfluidic device.