A　new　series　of　zinc(II)　phthalocyanine　derivatives　have　been　synthesized　and　characterized.　These　macrocycles　exhibited　a　sharp　absorption　band　in　the　red　visible　region　in　DMF,　which　indicated　that　they　were　dissolved　well　and　almost　did　not　aggregate　in　this　solvent.　Compared　with　the　unsubstituted　zinc(II)　phthalocyanine,　all　these　phthalocyanines　have　a　red-shifted　Q:band　(at　678-699　vs　670　nm)　and　exhibit　a　relatively　weaker　fluorescence　emission　and　a　higher　efficiency　at　generating　singlet　oxygen.　The　monosubstituted　photosensitizers　also　exhibit　high　photocytotoxicity　toward　HepG2　human　hepatocarcinoma　cells　with　IC50　values　as　low　as　0.02-0.05　mu　M　(lambda　=　670　am,　80　mW.cm(-2),　1.5　J.cm(-2)).　The　high　photodynamic　activities　of　these　compounds　are　in　accordance　with　their　low　aggregation　tendency　and　high　cellular　uptake.　Their　structure-activity　relationship　was　assessed　by　determining　the　photophysical　properties,　cellular　uptake,　and　in　vitro　photodynamic　activities　of　this　series　of　compounds.　As　shown　by　confocal　microscopy,　monosubstituted　phthalocyanines　can　target　the　mitochondria　and　lysosomes　of　the　cells,　and　tetrasubstituted　phthalocyanines　tend　to　target　the　lysosomes　of　the　cells.