As　widespread　organic　pollutants　in　the　environment,　polycyclic　aromatic　hydrocarbons　(PAHs)　greatly　threaten　human　health.　The　adsorption　technology　has　become　one　of　the　main　methods　to　deal　with　PAHs　because　of　its　low　cost,　simple　design,　and　no　secondary　pollution.　Among　them,　solid　media　have　strong　adsorption　capacities　for　PAHs　and　are　widely　used.　In　this　work,　activated　carbon　was　chosen　as　the　solid　adsorbent.　The　adsorption　behavior　of　three　PAHs　(naphthalene,　anthracene,　and　phenanthrene)　on　activated　carbon　was　investigated　at　the　molecular　level　by　Grand　Canonical　Monte　Carlo　(GCMC)　method.　The　effects　of　different　functional　groups　(amino,　carboxyl,　hydroxyl,　carbonyl,　and　hydrogen　groups)　and　temperature　effect　on　the　adsorption　isotherms　and　heat　of　adsorption　of　PAHs　on　activated　carbon　were　calculated.　The　results　showed　that　the　carbonyl　functional　group　increased　the　adsorption　of　PAH　molecules　by　the　most　considerable　amount　among　all　the　functional　groups.　Acid　functional　groups　were　more　favorable　to　the　adsorption　of　PAHs　than　alkali　functional　groups.　The　adsorption　capacity　and　heat　of　adsorption　of　PAHs　decreased　when　the　temperature　increased.　The　adsorption　performance　of　bicyclic　aromatic　hydrocarbons　was　more　influenced　by　temperature　than　that　of　tricyclic　aromatic　hydrocarbons.