Micrometer sized multi-hollow spheres of epoxy resin were prepared by a physical method so-called phase inversion emulsification technique. The formation mechanism of the titled spheres was studied by incomplete phase inversion. The requisite for the formation of multi-hollow spheres was that irreversible coalescence among the water droplets under shear action before the phase inversion point existed. This process could be facilitated by a lower emulsifier concentration and a higher emulsification temperature. Moreover, a theoretical explanation of the formation of the title spheres was presented.