To　develop　a　highly　efficient　photosensitizer　for　photodynamic　therapy　(PDT),　we　have　designed　and　synthesized　a　phthalocyanine-lactose　conjugate　(Pc-Lac)　through　axial　modification　of　silicon(IV)　phthalocyanine　with　lactose　moieties.　With　the　lactose　substituents,　Pc-Lac　is　highly　hydrophilic　and　non-aggregated　with　efficient　reactive　oxygen　species　(ROS)　generation　in　aqueous　media.　With　these　desirable　properties,　Pc-Lac　shows　high　photocytotoxicity　and　cellular　uptake　toward　HepG2　cells.　In　addition,　in　vivo　fluorescence　imaging　shows　that　Pc-Lac　could　selectively　remain　at　tumor　site,　leading　to　its　enhanced　photodynamic　efficacy　against　H22　tumorbearing　mice.　Therefore,　Pc-Lac　shows　a　great　potential　as　a　highly　efficient　molecular　photosensitizer　for　PDT.