Silicon secondary crosslinked interpenetrating polymer networks (IPNs) of poly(methyl acrylate-co-hydroxylethyl acrylate) (PMA-HEA) and SiO2 were prepared and characterized. The effects of composition, water content and substrate plate on the phase morphology of the IPNs of PMA-HEA/SiO2 were studied by SEM, and the T-g measured by d.s.c. The broadening of the transition region was observed with the increase of water content and the prolongation of the reflux time, and the tendency of the aggregation of silicon in the surface and bottom was also observed with Teflon as a substrate plate. However, an optically transparent film was easily achieved at higher temperature due to the chemical crosslink and physical entanglement between the two phases of PMA-HEA and SiO2.