Regular polysulfone (PSF) honeycomb film with micron-sized cells was prepared by casting the solution in an atmosphere with high humidity. Water droplets acted as the template around which the PSF in the solution assemble. In this paper, the effects of atmosphere humidity, solution concentration, and the PSF molecular weight on pore size were discussed; the influence of storage time of casting solution on the pattern regularity was presented; the mechanism of pattern formation was proposed. (C) 2005 Elsevier Ltd. All rights reserved.