Protoporphyrin IX (PpIX), which is an efficient photosensitive agent, cannot be used directly in photodynamic therapy due to its aggregation in physiological environment. If PpIX is made water-soluble without losing its photosensitive properties, it can be used in many medical fields, including cancer treatment. Here we report synthesis of PpIX homologue with mPEG550 (Porfipeg) and its photodynamic effects on both in-vitro and in-vivo environment. Porfipeg is synthesized to give PpIX the ability to dissolve in water. Spectrometric (FT-IR, NMR, MS, UV-vis and Fluorescence) measurements were performed. Porfipeg can penetrate into the cells and indicates no cytotoxicity in the dark whereas cell viability significantly reduced with light irradiation. The cells can be visualized by fluorescence microscope. In-vivo experiment revealed that intravenous injection of Porfipeg is more efficient than intraperitoneal injection for the acute photodynamic effects within 30 min. Moreover it is excreted by the kidneys. In conclusion, Porfipeg has remarkable potentials to be used in both fluorescence guidance in surgeries and photodynamic therapy for cancer treatment.