The main study of this experiment focuses on enzymology characteristics of natto kinase, by use of Bacillus natto HW236- 5 isolated and named by Institute of Microbiology. Bacillus natto HW236- 5 was obtained from extraction and separation of fermented soybean.By methods of SDS- PAGE and Zeta Potentiometry, it respectively measured that the molecular weight of natto kinase is 28 k Da, isoelectric point is 8.58,enzyme activity of natto kinase is 62520 U/g. When natto kinase is in different temperature, it finds out that the higher is the temperature, the lower is its enzyme activity. When Na Cl concentration is lower than 1.35 mol/L, it plays promoting effects on enzyme activity of natto kinase. On the contrary, it is higher than 1.35 mol/L, the enzyme activity of natto kinas is inhibited.