Vitreoscilla is a gram-negative bacterium that contains a unique bacterial hemoglobin and grows very well under the condition of low oxygen concentration. It also contain a bacterial catalase to be not correspond with another species on genus Beggiatoa. The primary function of Vitreoscilla catalase may be to remove hydrogen peroxide produced by ViWb oxidation. The molecular size of the catalase was estimated to be approximately 250,000 Da. The subunit structure of this enzyme may be A₂B₂ (A : MW 64,000 Da, B : MW 58,000 Da) but is not clear in the research reported here. Optimum pH is 7.0∼8.0 for catalase activity and Soret peak on absorption spectra of oxidized catalase is represented in 406 ㎚ and Soret peak of reduced form from sodium dithionite moved at 442 ㎚. Vitreoscilla catalase is unstable a high tempernture, and its Michealis constant, K_m was 0.016 M hydrogen peroxide. The turnover number of the enzyme was 25,000 mol. The 0.25 mM potassium cyanide was competitive inhibitor and the dissociation constant of the enzyme-inhibitor complex was 0.67 mM. N-terminal amino acid sequences of two subunits are determined for the probe synthesis using to the cloning of Vitreoscilla catalase gene.