In this paper, the photodynamic effects df hematoporphyrin, Y-Hpd (which is prepared by Yangzhou Biochemical Pharmaceutical Co.) and photofrin-Ⅱ on S 180 tumour cells and HeLa cells were compared, with each other the concentration of three porphyrins in S 180 tumour cells or liposome were assayed after cellular uptake. In vitro the photodynamic cell killing activity of Y-Hpd was signficantly higher than that of hematoporphyrin and photo-frin-Ⅱ, their biological activity order is as follows: Y-Hpd, photofrin-II, hematoporphyrin. Comparing with hematoporphyrin, photofrin-Ⅱ, the concentration of Y-Hpd was the highest in S 180 tumour cells or liposome. It is indicated the level of porphyrins in cells is one of the important factors for evaluating their biological activity.