To evaluate the biocompatibility of polymethylmethacrylate(PMMA) denture base resin containing silver-supported antimicrobial agent STR-1 of nanometer level in vitro.According to the national standards for biological evaluation of dental materials, the cytotoxicity of denture base resin containing STR-1 at concentrations of 5 g/L and 10 g/L was examined by molecular filtrating method, and the hemolysis of STR-1, denture base resin containing STR-1 at concentrations of 5 g/L and 10 g/L was also surveyed.The control denture base resin without containing STR-1 and the denture base resins containing STR-1 at concentrations of 5 g/L and 10 g/L were not cytotoxic to L929 cells. Two hours and 24 hours after cell culturing, the filter membranes of the control and experimental groups were stained evenly with blue color. The staining intensity was not decreased and the fading areas were 0 mm2 during the culturing. The cytotoxicity grades were 0. The hemolysis rates of the antimicrobial agent STR-1 and the denture base resins containing STR-1 at concentrations of 5 g/L and 10 g/L were 1.7%, 3.5% and 3.7% respectively. They were less than the national guild standard 5% which represent no hemolysis.The PMMA denture base resins containing silver-supported antimicrobial agents STR-1 of nanometer level at concentrations of 5 g/L and 10 g/L exhibit good biocompatibility.