The Annexin A4 gene was cloned from the Grass Carp(Ctenopharyngodon idellus) liver and kidney cDNA library.The full sequence was 1 307 bp,containing a 5' untranslated region of 104 bp and a 3' untranslated region of 237 bp.The open reading frame was 966 bp which could code a 321 amino acids peptide.The Grass Crap Annexin A4 had a tail(N-terminal region) and a core domain(C-terminal region).The N-terminus was composed of 15 residues.The core domain was made up of four similar repeats,each covering a type Ⅱ calcium binding site.And there was a KGD motif in the fourth site.The Grass Crap Annexin A4 had a high expression level in the liver,kidney,spleen,heart,gill and intestine,but its expression was not detected in the muscle and brain.Additionally,down-regulated expression of Annexin A4 was detected in all of the six tissues after Grass Carp was challenged by Poly Ⅰ:C.Phylogenetic tree analysis revealed that Grass Carp Annexin A4 shared the highest homology with that of Zebra Fish(Danio rerio).Positive selection sites were not detected by adaptive evolutional analysis,and therefore Annexin A4 might be highly conserved and have strong functional constraint.