Abstract: Phycocyanin subunits liposomes (PCS-lip) were prepared and its cellular uptake and photodynamic therapy (PDT) effect on cancer cells were studied. In the experiment, film dispersion method was used to prepare phycocyanin subunits liposomes; particle size and distribution were detected by zetasizer and transmission electric microscope; the effects of liposome as carrier on cell uptake in vitro were evaluated in S180 by using fluorescence microscope; and photodynamic therapy effect was assessed with MTT method. As shown in the results, the particle size mainly ranged from 80 nm to 160 nm, and average encapsulation rate was 42.3%. In the concentration of 100 μg·mL^-1, transfection rate reached (18.5±0.8)% at 2 h, (23.1±0.9)% at 4 h, keeping a balance in 5-6 h, and its photodynamic therapy effect in vitro improved with the increasing of concentration of phycocyanin subunits liposomes. In the concentration of 200 μg·mL^-1, cell survival rate of BGC-823 and S180 reached (45±5.2)% and (36±5.5)%, respectively, and the cell survival rate differentiation between PCS-PDT group and PCS-lip-PDT group reached 7%-11% (P<0.05). In this study film dispersion method could keep the biological activity of phycocyanin subunits very well. Phycocyanin subunits liposomes will transfect cells more quickly than phycocyanin subunits in the same concentration, and in the same conditions, phycocyanin subunits liposomes have the better PDT effect on cancer cells as they were incubated with cells for 4 h.