By　treating　Al4C3　as　the　precursor　and　growth　environment,　graphene　nanosheets　(GNs)　can　efficiently　be　derived　from　coal-tar　pitch,　which　has　the　advantages　of　simple　preparation　process,　high　product　quality,　green　environmental　protection,　low　equipment　requirements　and　low　preparation　cost.　However,　the　defects　in　the　prepared　GNs　have　not　been　well　understood.　In　order　to　optimize　the　preparation　process,　based　on　density　functional　theory　calculations,　the　influence　mechanism　of　Al-O　and　Al-C　clusters　on　defects　in　GNs　derived　from　coal-tar　pitch　via　Al4C3　precursor　has　been　systematically　investigated.　With　minute　quantities　of　oxygen-containing　defects,　Al-O　and　Al-C　clusters　have　been　realized　in　the　prepared　GNs　from　X-ray　photoelectron　spectroscopy　analysis.　Therefore,　the　influences　of　Al-O　and　Al-C　clusters　on　graphene　with　vacancy　defects　and　oxygen-containing　defects　are　systematically　explored　from　theoretical　energy,　electron　localization　function　and　charge　transfer　analysis.　It　is　noted　that　the　remaining　Al-O　and　Al-C　clusters　in　GNs　are　inevitably　from　the　thermodynamics　point　of　view.　On　the　other　hand,　the　existence　of　defects　is　beneficial　for　the　further　adsorption　of　Al-O　and　Al-C　clusters　in　GNs.　©　2022　by　the　authors.