This study reports the purification and biochemical characterization of thermostable and acidic-pH-stable α-amylase from Bacillus sp. Iranian S1 isolated from the desert soil (Gandom-e-Beryan in Lut desert, Iran). Amylase production was found to be growth associated. Maximum enzyme production was in exponential phase with activity 2.93 U ml-1 at 50°C and pH 5. The enzyme was purified by isopropanol sedimentation, ion-exchange chromatography on DEAE cellulose DE-52 and gel filtration on Sephadex G-100. The enzyme was purified to homogeneity with purification fold 98.9 with 25% yield and specific activity 375.9 U mg-1 of protein. The molecular weight of purified α-amylase was estimated to be 70 KDa by SDS-PAGE. The enzyme remained stable in a wide range of temperature and pH between 30°C- 110°C and 3-9, respectively. Assayed with soluble starch as substrate, the enzyme displayed optimal activity at 90°C and pH 5. The purified α-amylase was acid- and thermo-stable with novel properties making it suitable for many industrial purposes.