A targeting and water-soluble photosensitizer folate-PEG-chlorin (I) has been synthesized and characterized. The uptake of conjugate I by HeLa and Hep-2 cells was much higher than the uptake by A549 cells, and can be inhibited by folic acid. Conjugate I exhibited much lower cytotoxicity against HeLa and Hep-2 cells but significant photocytotoxicity. Conjugate I preferentially located in mitochondria of the Hep-2 cells, and conjugate I-PDT induced a loss of mitochondrial membrane potential and then the apoptosis of Hep-2 cells.