To　improve　the　aqueous　solubility　and　cancer　targeting　of　the　photosensitizers　in　photodynamic　therapy　(PDT),　we　encapsulated　the　photosensitizer　in　a　biocompatibility　and　pH-sensitive　drug　delivery　system,　zeolitic　imidazolate　frameworks-8　(ZIF-8)　nanospheres.　Powder　X-ray　diffraction　and　electron　microscopy　show　that　our　nanospheres　are　uniform　and　single-crystalline　particles.　Owing　to　the　cleavage　of　zinc-ligand　coordination　bonds,　more　ZnPc-COOH　were　released　much　faster　in　the　mild　acidic　conditions　(pH　5.0　and　6.0)　in　comparison　with　physiological　environment　(pH　7.4).　By　incorporating　ZnPc-COOH　in　ZIF-8,　our　nanospheres　exhibited　high　singlet　oxygen　quantum　yield　and　intracellular　ROS　generation.　Cell　viability　experiments　toward　HepG2　cells　demonstrated　the　low　toxicity　of　ZIF-8　and　the　good　anticancer　efficacy　of　the　nanospheres　with　low　IC50　values　(4.2-4.9　mu　g/mL)　under　light　illumination　(670　nm,　1.5　J/cm(2)).　Collectively,　these　results　suggested　that　our　nanospheres　are　the　promising　pH-responsive　drug　delivery　systems　for　PDT.