Abstract: Using rapid amplication of cDNA ends (RACE-PCR), a 1.5 kb cDNA encoding chitin deacetylase 1 protein SeCDA1 was cloned from Spodoptera exigua. The gene secda1 was further cloned into pPIC9K and transformed into E.coli JM109 competent cells. The recombinant plasmid was named pPIC9K-secda1. Then the recombinant plasmid was linearized and transformed into Pichia pastoris GS115 competent cells by electroporation. Antibodies reacting to the recombinant SeCDA1 recognized a single protein by Western blot analysis after induction by methanol. The result indicated SeCDA1 was expressed in the yeast. The CDA activity of recombinant SeCDA1 is 1.35 U/mL. Transcription analysis on secda1 sequence during various developmental stages and in different tissues by RT-PCR showed that secda1 was expressed in head, midgut, integument, malpighian tubules, fat body and pupa. The expression of recombinant SeCDA1 laid the foundation for further investigation and physiological function of the SeCDA1 protein, and provided a theoretical basis for the biocontrol of Spodoptera exigua targeting CDA protein.