Thermo-tolerant phytase has lots of applications in different industries, such as environmental protection, aquaculture, and agriculture. In the present study, Bacillus sp. Dm018 has been isolated from Demand hot spring in Jiroft, which placed in the southwest of Iran. Statistical optimization approach by response surface methodology (RSM) leads to 2.3-fold growth in phytase construction by Bacillus sp. Dm018. The optimal temperature for phytase function was established to be about 60 degrees C. Furthermore the enzyme reserved more than 70% of its activity over an extensive pH series of 4.0-8. 0. Results showed that Dm018 phytase activity was inhibited by CaCl2 (5 mM) about 60%. Phytase activity was inhibited by SDS (5 mM) about 30% and slightly improved by EDTA about 6.0%. Phytase stability data exhibited that the enzyme reserved more than 50% of it,s original activity after pre-incubated in the existence of diverse ions, except CaCl2. These results indicate that Dm018 phytase has good latent for commercial attention as an animal feed preservative.