A new silane-based nanocomposite coating is proposed. Based on molecular dynamics simulation results, it is confirmed that the introduction of dopamine can greatly reduce the transport ability of salt solution in the micro-nano channels of silane coating and the movement ability of water molecules and ions at the interface of the composite coating. For the graphene oxide-silane coating, water molecules can diffuse into the silane layer and form hydrogen bonds with the hydrophilic ends of the silane molecules. The extreme grafted graphene oxide-dopamine-silane composite coating can fully utilize the hydrophobic property of silane molecules and completely block the water molecules from entering the silane layer, reducing the water molecule transport depth by 87.5%.