The　pentagonal　ZnO2　(penta-ZnO2)　monolayer　is　a　new　class　of　two-dimensional　materials　with　unique　properties,　which　are　still　largely　unknown.　This　work　studies　the　stability　of　the　geometries,　and　the　modulation　of　the　electronic,　magnetic　and　optical　properties　of　penta-ZnO2　doped　with　3d　transition　metal　(TM)　(Fe,　Co,　and　Ni)　atoms　replacing　the　host　Zn　atoms　by　using　first-principles　calculations.　The　structural　optimization　implies　that　all　these　three　atomic　species　can　be　effectively　doped　in　the　penta-ZnO2　monolayer,　due　to　the　strong　hybridization　of　TM　3d　and　O　2p　states　electrons.　Furthermore,　it　is　found　that　the　electronic　structures　and　optical　properties　are　tuned　by　the　doping　TM　atoms.　The　doping　of　TM　atoms　introduces　the　reduction　of　the　band　gap　energy,　and　Fe　and　Co　atoms　even　endow　magnetization　to　the　penta-ZnO2.　In　addition,　the　absorption　edges　of　all　the　three　doped　systems　exhibit　an　obvious　red　shift,　which　can　enhance　the　effective　utilization　of　the　solar　spectrum　in　the　visible　light　region.　This　study　gives　us　an　insight　in　the　physical　properties　of　the　TM　doped　penta-ZnO2　monolayer,　which　could　be　helpful　in　realizing　their　diverse　potentials　in　spintronic　and　photovoltaic　applications.