Purification of glutathione S-transferase (GST) in the 5th nymphs of Locusta migratoria manilensis (Meyen) was conducted by ammonium sulfate fractionation and reduced glutathione affinity chromatography. The results showed that GST activity could be detected in every ammonium sulfate fractionation segment, but higher activity was detected under the saturation degree of 55%～100%, and thehighest activity was found under 70%～85%. The specific activity determined with1-chloro-2, 4-dinitrobenzene (CDNB) and GSH as the substrates was 420.33 μmol/min/mg protein, and the purification factor was 18.86-fold. A GST was purified 61.25fold by using 60%～90% saturation ammonium sulfate precipitation followed by reduced glutathione affinity chromatography. The specific activity was 1 365.29 μmol/min/mg protein. SDS-PAGE showed that the molecular weight of the subunit was 24.4 kDa.