HWAP-Ⅰ is a peptide neurotoxin purified from the crude venom of the Chinese bird spider Selenocosmia humena, which has analgesic activity. According to the RT-PCR result, an artificial gene encoding HWAP-Ⅰwas chemically synthesized. The gene was then inserted into pPIC9K,a secretory expression vector for Pichia pastoris.The constructed pPIC9K-HWAP-Ⅰ was transformed into his⁴ mutant yeast GS115 and a Mut^s His⁺ cell line was screened.The recombinant HWAP-Ⅰwas secreted into the culture supernatant induced by 0.5% methanol.Tricine SDS-PAGE analysis indicated efficient expression and secretion of HWAP-Ⅰ.The molecular mass of product was about 4 ku. Yield of product was estimated to be 80 mg/L. Purified protein was assayed for biological activity and the results demonstrated that HWAP-Ⅰ had 60% analgesic activity compared to native HWAP-Ⅰ.