Clay-based　2D　nanofluidics　present　a　promising　avenue　for　osmotic　energy　harvesting　due　to　their　low　cost　and　straightforward　large-scale　preparation.　However,　a　comprehensive　understanding　of　ion　transport　mechanisms,　and　horizontal　and　vertical　transmission,　remains　incomplete.　By　employing　a　multiscale　approach　in　combination　of　first-principles　calculations　and　molecular　dynamics　simulations,　the　issue　of　how　transmission　directions　impact　on　the　clay-based　2D　nanofluidics　on　osmotic　energy　conversion　is　addressed.　It　is　indicated　that　the　selective　and　rapid　hopping　transport　of　cations　in　clay-based　2D　nanofluidics　is　facilitated　by　the　electrostatic　field　within　charged　nanochannels.　Furthermore,　horizontally　transported　nanofluidics　exhibited　stronger　ion　fluxes,　higher　ion　transport　efficiencies,　and　lower　transmembrane　energy　barriers　compared　to　vertically　transported　ones.　Therefore,　adjusting　the　ion　transport　pathways　between　artificial　seawater　and　river　water　resulted　in　an　increase　in　osmotic　power　output　from　2.8　to　5.3　W　m-2,　surpassing　the　commercial　benchmark　(5　W　m-2).　This　work　enhanced　the　understanding　of　ion　transport　pathways　in　clay-based　2D　nanofluidics,　advancing　the　practical　applications　of　osmotic　energy　harvesting.