Abstract: Fish L-amino acid oxidase (LAAO) has a strong killing effect on bacteria and parasites. In order to study the gene sequence characteristics and expression pattern of LAAO gene in grouper (Epinephelus coioides) post Cryptocaryon irritans infection, two LAAO cDNA sequences were identified and designated as EcLAAO-1 and EcLAAO-2. The ORF of EcLAAO-1 and EcLAAO-2 were 1536 bp and 1569 bp, coding 511 and 522 amino acids respectively. They both have Amino_oxidase domain and LAAO conserved sequences of DBM and GG motif. Multiple sequence alignment showed that EcLAAO-1 and EcLAAO-2 protein shared high sequence identity with LAAO of other teleost. EcLAAO-1 and EcLAAO-2 were clustered into the same subgroup with other teleost in the phylogenetic tree. EcLAAO-1 and EcLAAO-2 were widely distributed in various tissues, especially in skin, gill, thymus, liver and muscle. EcLAAO-1 and EcLAAO-2 were up-regulated in the gill and spleen post C. irritans infection. Together, these results suggest that LAAO might be involved in host’s innate immunity and play an important role in the defense against C. irritans infection.