Abstract: BmK AngM1 is a long-chain scorpion toxin purified from the venom of Buthus martensii Karsch. It has been reported to exhibit evident analgesic effect and low toxicity, and has the potential to be a novel analgesic drug. The BmK AngM1 gene was transformed into Pichia pastoris GS115. Mut⁺ and Mut^s recombinant strains were screened by phenotype and Mut⁺ recombinant strains were used to detect BmK AngM1 gene copy number in the real-time PCR. Expression of BmK AngM1 in the Mut⁺ recombinant strain was compared with that of the Mut^s recombinant strain with the same single copy of BmK AngM1 gene under the same condition. The results indicated that the transcription level of BmK AngM1 gene in the Mut^s recombinant strain was 2.7 fold of that in the Mut⁺ recombinant strain in the real-time PCR, and the expression of BmK AngM1 in the Mut^s recombinant strain was 1.5 fold of that in the Mut⁺ recombinant strain. Therefore, Mut^s recombinant strain showed better ability to express BmK AngM1 than Mut⁺ recombinant strain.