N-2-filled hollow glass beads (HGB) were first used as novel gas carriers to prepare microcellular polymers by compression molding. Dicumyl peroxide was acted as crosslink agent to control the produced microcellular structure of low density polyethylene (LDPE)/HGB. The effect of temperature, pressure and the content of gel on the embryo-foaming, and final-foaming structure are investigated. Scanning electronic microscopy shows that the average cell size of microcellular LDPE ranges from 0.1 to 10 mu m, and the foam density is about 10(9)-10(11) cells/cm(3). A clear correlation is established between preserving desirable micromorphologies of microcellular LDPE in different processing stage and tuning processing factors. The pertinent foaming mechanism of microcellular materials foamed with HGB is proposed. Because of the good mechanical strength, low density, weak water-absorption, and excellent heat insulate ability, microcellular LDPE has great potential application in energy building materials. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114:4030-4035, 2009