Abstract: Ruminants have the ability to utilize phytate phosphate by rumen microorganisms. Until now, domestic research on ruminal microbe phytase is insufficient. In this paper, phytase origin and activity in the rumen was briefly reviewed, and five kinds of rumen bacteria were capable of producing phytase. Among these bacteria, phytase activity was particularly prevalent in Selenomonas ruminantium (199.1703.6 U·mL-1). Based on their optimal pH and catalytic mechanisms, ruminal phytases are classified into acid phytase and cysteine phosphatases phytase, respectively. According to the stereospecificity of phytase, rumen microbes may exist 3phytase and 5phytase. Furthermore, kinetics of enzymatic reaction characteristics of phytases were summarized and discussed comprehensively. In a brief, phytase of S. ruminantium has a optimal temperature of 5055 ℃, an optimal pH range of 4.05.5, and exhibits the highest specificity constant for myoinositol hexakisphosphate and ATP. The optimal phytase activity of Megasphaera elsdenii is displayed at pH5.0 and 60 ℃, and it also displays strict specificity for myoinositol hexakisphosphate.