This paper presents a new computational method for simulating polymer network formation. There are four separate procedures involved in the methodology for this multiscale simulation: (i) mapping of the polymerizing monomers onto a coarse-grained model, (ii) cross-linking the monomers by applying Monte Carlo simulation to the coarse-grained model, (iii) reverse mapping of the coarse-grained model to a fully atomistic representation, and (iv) simulation of the atomistic model through standard molecular dynamics technique. Molecular dynamics simulations and experimental studies are carried out to check the algorithm on the basis of the determination of the physical properties of the cycloaliphatic epoxy resin which is prepared from 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate as resin monomers and 4-methylhexahydrophthalic anhydride as curing agents. Depending on the effective conversion and temperature, we determine the density, the glass transition temperature, and the thermal expansion coefficient of the cross-linked epoxy system. An increase in the degree of cross-linking is found to increase the glass transition temperature. Good agreement between computer simulation and experimental results is achieved for highly cross-linked networks, thereby showing that the simulation model is basically valid.