Abstract: The NADPH‐sulfite reductase from Escherichia coli was purified to electrophoretic homogeneity by ammonium sulfate fractionation, and DEAE Sephacel and Sephacryl S‐300 HR chromatography. The recovery and molecular weight were 31.7% and 119000, while the optimal pH and temperature for the activity were 7.7 and 25°C, respectively. It was strongly inhibited by PCMB, KCN, Hg2+, Fe2+, Fe3+, Ca2+, Co2+, and Cu2+, moderately by NEM, PMSF, IAA, Cd2+, Zn2+, Mn2+, and Ba2+. Addition of purified reductase significantly increased the reactive SH and gel strength of surimi prepared from frozen mackerel. The data suggest the high potential of microbial NADPH‐sulfite reductase in surimi processing using frozen fish or denatured muscle proteins as raw materials.