Aim to explore a potential treatment of AIDS-photodynamic therapy by detecting the photoinaction on hunman immunodeficiency virus (HIV) in vitro,mixed the photosensitizes hematoporphyrin monomethyl ether or methylene blue by a series of dilute strengths with the host cells MT4,C8166 or H9/HIV-1ⅢB or the virus HIV-1ⅢB for 2 hours incubation,followed by irradiation by a 630 nm semiconductor laser with energy density 0.3 J/cm2. After certain time,the activites against HIV-1ⅢB were assayed by determining the syncytial formation under the inverted microscope or MTT and measuring the p24 antigen expression level in supernatant by ELISA. Results show PDT inhibited the cell-cell fusion (inhibition rate,HMME-PDT64.68%,MB-PDT61.56%)and virus-cell fusion (inhibition rate,HMME-PDT 85%,MB-PDT 73.64% )induced by HIV-1ⅢB significantly,and had an intensive inactivation on the cell-free HIV-1ⅢB especially the inhibition rate up to 100%. However,PDT had no effect on the replication course 2 hours after cute infection or chronic infection of HIV-1ⅢB. Therefor PDT has outstanding inhibition on cell-free HIV-1ⅢB and fusion induced by HIV-1ⅢB,which prompts PDT may be a new treatment of AIDS in future.