This study investigated the physicochemical properties changed during the black soybean natto process which including the soaking, steaming, and fermented procedures. Results showed that fermented procedure significantly increased the moisture, viscosity and color (L, a and b value). On the other hand, steaming procedure significantly decreased the hardness of black soybean. After steaming and fermented, TCA-soluble nitrogen and ammonia nitrogen contents significantly increased, however, the solubilization ratio of protein will decreased first after steaming then increased after fermented. The final product own the strongest scavenging effect of DPPH among all treatments, but the contents of polyphenol compounds were increased after soaking and cooking procedure, then decreased after fermentation. The steaming procedure significantly decreased the contents of anthocyanin and isoflavone.