In　this　paper,　a　solar-blind　ultraviolet　photodetector　(PD)　based　on　the　graphene/vertical　Ga2O3　nanowire　array　heterojunction　was　proposed　and　demonstrated.　To　the　best　of　our　knowledge,　it　is　the　first　time　that　vertical　Ga2O3　nanowire　arrays　have　been　realized.　Ga2O3　nanowires　were　obtained　by　thermally　oxidizing　GaN　nanowires　grown　by　molecular　beam　epitaxy　on　n-doped　Si　substrate.　Then,　a　monolayer　graphene　film　was　transferred　to　Ga2O3　nanowires　to　form　the　graphene/vertical　Ga2O3　nanowire　array　heterojunction　and　transparent　electrodes.　The　fabricated　device　exhibited　a　responsivity　(R)　of　0.185　A/W　and　rejection　ratio　(R258　nm/R365　nm)　of　3x10(4)　at　the　bias　of　-5　V.　Moreover,　the　fast　response　times　of　this　PD　were　9　and　8　ms　for　the　rise　and　decay　times　under　254　nm　illumination,　respectively,　which　are　attributed　to　the　unique　properties　of　nanowire　arrays　and　the　graphene/vertical　Ga2O3　nanowire　array　heterojunction　structure.