Abstract: A hydrogenase has been purified by DE-52(1), Sephadex G-75, DE-52(2) and Sephadex G-100 from Spirulina platensis, showing one band on SDS-PAGE. Overall purification of about 200-fold was achieved with 14% recovery of enzyme activity.The average molecular weight of hydrogenase was 56kd identified by SDS-PAGE.The isoelectric point determined by isoelectric focusing electrophoresis was pH4.2. Analysis of amino acid composition indicated that hydrogenase consists of 456 amino acid residues, being rich in aspartic acid and glutamic acid. It was an iron-sulfer protein identified by absorption spectrum. The enzyme was able to catalyze hydrogen evolution in the presence of MV reduced by dithionite. The Km (MV) of hydrogenase was 0.31mmol/L. Its optimum pH was 7.5-8.0.