Abstract: To investigate the structure and biological function of inositol-requiring enzyme 1(IRE1), an endoplasmic reticulum stress-related gene, and its role in response to MC-LR, the full-length cDNA sequence of grass carp IRE1-like gene was cloned basing on the EST sequence of IRE1-like members from transcriptome sequencing results of grass carp by using RACE technology (GenBank: MG797683). The total length of IRE1-like gene was 3595 bp, including 3093 bp open reading frame encoding 1030 amino acids. Its molecular weight was 116.2 kD with a theoretical isoelectric point of 6.26, and it has transmembrane structure and signal peptide with three structural domains, including Luminal domain (39—307 aa), STKc domain (569—834 aa) and RNase domain (837—915 aa). The results of homology and phylogenetic tree indicated that grass carp IRE1-like was most related to Danio rerio IRE1-α. The results of quantitative RT-PCR (qRT-PCR) showed that grass carp IRE1-like gene highly express in liver, and also modestly express in other tissues, such as muscle, spleen, gill and heart. MC-LR significantly induced the expression of grass carp IRE1-like gene in 25 μg Mc-LR /kg BW and 100 μg MC-LR /kg BW group at 24h and 96h, respectively. Grass carp IRE1-like gene may play an important role in MC-LR-induced endoplasmic reticulum stress, laying a foundation for further study on the function of grass carp IRE1-like gene.