The mechanical properties of Epon-862 crosslinked with curing agent DETDA were simulated using a molecular dynamics code named GPIUTMD fully developed on multi graphical processing units. A new algorithm was proposed to simulate the cross-linking process during the chemical interaction of epoxy with the curing agent without changing the bond data. The models were created by densely packing preconstructed oligomers of different composition and compact them into the periodic simulation box. The properties of interest predicted by the molecular dynamics method were density, glass transition temperature and bulk modulus and found to be in good agreement with available data in the literature. Also, a study on the optimal ratio of resin to cure agent was carried out, and the results showed that, with a 3.6 mix mass ratio, the composite is in its strongest mechanical and structural state.