Abstract： Objective To investigate the anti-tumor effects of photodynamie therapy(PDT)on human pancreatic cancer xenograft in nude mice and the time-effect relationship of PDT.Methods The animal model of human pancreatic cancer was developed by suturing small pieces of SW1990 tumors into the dorsum of nude mice.When the size of the tumors increased to 0.8～1.0 cm.36 mice were randomly divided into three groups:control group(no treatment),photosensitizer group(Photosan 2mg/kg,abdominal cavity injection),photodynamic group(Photosan 2 mg/kg injection+laser irradiation).Each group included 12 mice.The tumor sizes were measured twice per week and the weight8 and volumes of the tumors were measured,and the tumor inhibitory rate was calculated three weeks later.Results The tumor volume of photodynamic group was (0.22±0.12)mm3 at the 6th day,which was significantly smaller than(0.43 s0.18)mm3 of control group and(0.39±0.15)mm3 of photosensitizer group(P＜0.05).15 days later,the tumor volumes of PDT groups increased.21 days later.the weight of the tumors in photodynamie group was(0.69±0.23)g,which was significantly lower than(1.65 ±0.21)g of control group and(1.62±0.12)g of photosensitizer group(P＜0.05).The tumor inhibitory rate in photodynamic group was 58.18%,which was significantly higher than that of photoseasitizer group(1.8%,P＜0.05).Conclusions Photodynamie therapy had significant anti-tumor effect on human pancreatic cancer with quick-acting efficacy,but photodynamie therapy alone exeaed efficacy only in the shoa term.