Objectives: New photosensitizer 9-hydroxypheophorbide-$alpha$(9-HpbD-$alpha$) was derived from chlorophyll in water with peak absorption at 660nm. 9-HpbD-$alpha$ was tested with 660 nm diode laser for the anticancer effect of photodynamic therapy. Materials and Methods: Human SNU 1041 cells were seeded into 96 well plate at a density of $$ cells/well for 24 hours. Cells were washed with media containing various concentration of 9-HpbD-$alpha$ ranging from $0{mu}g/ml;to;3.75{mu}g/ml$. Then, laser treatment was done with 660nm diode laser ($10mW/cm^2$) at various time setting (0, 30, 60, 90, 120 minutes) and with various time interval (0, 1, 4, 6, 18 hours). The treated cells were incubated 48 hours and MTT assay was done to measure the viability of cells. Results: The viability of cells was more than 90% after laser treatment in control group. The viability of cells was decreased with increasing concentration of 9-HpbD-$alpha$ and laser treatment time in experimental groups. The viability of cells was decreased significantly as the interval time between addition of 9-HpbD-$alpha$ and laser irradiation was increased. Conclusion: This study shows the anticancer effect of photodynamic therapy using 9-HpbD-$alpha$ and 660nm Diode laser on carcinoma cell line. 9-HpbD-$alpha$ is considerd as one of new photo sensitizers in the field of photodynamic therapy.