Corrosion protection is one of the most important issues when copper is applied in power electronics packaging as bonding wire, die attachment, interconnection, and DBC substrate. Covering a layer of corrosion-resistant encapsulation material is a worthy consideration to protect copper. In this paper, the corrosion-resistant effects of two organic encapsulation materials, polydimethylsiloxane (PDMS) and hexamethyldisiloxane (HMDSO), on the copper surface were performed by molecular dynamics simulations. Firstly, the Cu-coating bilayer models were constructed, and the binding performances of the encapsulation material/copper interface were evaluated through calculating their interaction energy, proving that the organic coatings can form interconnection on copper surface. Then, the diffusion processes of corrosive gas molecules (H₂S, H₂O and O₂) into the copper layer under different coating conditions were simulated, and both coatings exhibited good corrosion protection performances. The above results indicate that both PDMS and HMDSO have promising potential for copper corrosion protection in power electronics packaging. This may provide some guidance for corrosion protection of copper material used in power electronics packaging.