In order to determine the effective bactericidal concentration of hydrogen peroxide, Salmonella enterica serovar Typhimurium was used as a target microorganism to explore the effect of hydrogen peroxide on activity and culturability of it in tap water and its viable but non-culturable (VBNC) state by means of molecular biology. The results showed that lower hydrogen peroxide concentration (0～15 mmol/L) could kill some S. Typhimurium, which could be completely sterilized with 1 mol/L hydrogen peroxide. It was also found that 4.08 lg(CFU/mL) S. Typhimurium could be induced into a VBNC state as exposure to 15 mmol/L hydrogen peroxide. The morphology and structure of S. Typhimurium in VBNC state have changed, and the catalase, superoxide dismutase and glutathioneperoxidase were almost completely inactivated. It was detected that the intensity of free radicals generated during treatment was positively correlated with VBNC indexes within 0～30 min.