Based on the codon bias of Pichia pastoris,the gene encoding a thermoacidophilic α-amylase BD5088 was modified for the optimal expression in P.pastoris.The gene was cloned into the vector of pPIC9K to produce the recombinant vector pPIC9K-BD5088 and then transformed into chromosome of P.pastoris GS115 strain.Regulated by the α-factor,promoter of AOX1 gene and termination signal of yeast genomic,the recombinant α-amylase PrBD5088 was expressed and secreted into the culture with a max yield of 200 mg/L after 5 days induction.Comparing to the recombinant amylase ErBD5088 expressed by E.coli,the optimum temperature of PrBD5088 increased from 80℃ to 90℃.Although the optimum pH of PrBD5088 was same to ErBD5088,but PrBD5088 have more broad stable range of pH than ErBD5088.More than 50% of its maximal activity was retained in the pH 4.0~8.0 of PrBD5088 and pH 5.0~7.0 of ErBD5088.The PrBD5088 is so thermostable that over 80 % of its activities was retained after disposed at 100℃ for 1 h.But the half-life of ErBD5088 at 100℃,pH5.6 was only 20 min.High concentration of Zn2+ and Ca2+ slightly increased its activity,while Cu2+ partially inhibited its activity at high concentration.SDS-PAGE result showed the molecular weight of PrBD5088 was about 56 ku,which was bigger than the calculated molecular mass 49 ku of ErBD5088.PrBD5088 is not modified by N-linked glycosylation but by O-linked glycosylation.The O-linked glycosylation had influence on thermostability,the optimal temperature and optimal pH range of PrBD5088.