In order to explore the molecular characteristics of the interleukin-22 （IL-22） gene in channel catfish （Ictalurus punctatus） and its response to different pathogenic microorganisms，the coding sequence （CDS） of IL?22 was cloned by PCR amplification，and the distribution of IL?22 mRNA in different tissues and under different stimulate were monitored by quantitative real-time PCR （qRT-PCR）.The results showed that the CDS of IL?22 was 534 bp in length and encoded 177 amino acids.Multiple alignment and analysis of amino acid sequence showed that IL?22 was highly conserved in evolution of fish and vertebrates.qRT-PCR results showed that IL?22 was widely distributed in 10 tissues of channel catfish，with the highest expression in the hindgut and the lowest in the heart.After stimulation for 24-48 h，IL?22 was up-regulated by Poly（I：C） and LPS stimulation，and down-regulated by PHA and PMA stimulation in the channel catfish kidney cells.The bacteria，virus injection and cypermethrin immersion experiments showed that the expression of IL?22 in the gill，skin，hindgut，spleen，trunk kidney and head kidney was up-regulated overall.The above results showed that the expression patterns of IL?22 in different tissues under different stimulate are different，and this gene can participate and play a key role in mucosal and various immune responses.