Band　alignment　has　been　keeping　fascinating　because　of　its　importance　to　the　heterojunction　interface　for　engineering　the　device　performances.　One　of　the　most　crucial　parameters　to　determine　band　alignment　is　the　charge　neutrality　level　(CNL).　In　this　study,　we　experimentally　investigate　the　CNL　modulation　from　the　perspective　of　dipole　formation　at　the　GeO2/Al2O3　interface　and　conduction　band　offset　(CBO)　tendency　with　Al2O3　thicknesses　after　post-deposition　annealing　(PDA).　The　core　level　shift　at　the　GeO2/Al2O3　interface　consists　with　the　dipole　change　for　the　as-grown　and　N-2　PDA　samples.　The　origin　of　dipole　change　after　PDA　is　explained　through　CNL　theory　and　band　alignment.　The　CNL　modulation　is　certified　from　the　CBO　dependence　on　the　Al2O3　thickness.　The　CBO　at　Ge/Al2O3　hetero-interface　decreases　with　Al2O3　thickness　for　the　as-grown　sample　and　increases　with　Al2O3　thickness　after　N-2　annealing.　The　CNL　was　experimentally　estimated　as　4.57　and　3.52　eV　above　the　Al2O3　valence　band　maximum　for　the　as-grown　and　N-2　PDA　samples.　The　CNL　estimation　is　also　consistent　with　the　modulation　change　of　dipole　at　the　Al2O3/GeO2　interface　and　CBO　at　Ge/Al2O3　interface.　This　research　may　provide　a　feasible　method　of　promoting　device　performance　by　modulating　the　CNL　of　dielectrics.