In this report, streptavidin (SA) was further identified on the basis of our previous researches in SA isolation and purification. 23.2 mg of SA productivity could be obtained after purification by DEAE-52 column from 1 L of culture supernatant. The spectrum scanning of ultraviolet absorption was congruent with that of the Sigma product. 2 bands appeared on the SDS-PAGE electrophoresis of SA. The molecular weight of SA was 72 881 Dalton with PI 6.0; the averaged biotin-binding activity was 18 micrograms/mg. The results confirmed that the methods of isolation and purification of SA developed by authors were reliable for immunological application.