Abstract: One prothrombinlike gene is cloned for the first time from large yellow croaker (Pseudosciaena crocea) by utilizing rapid amplification of cDNA ends (RACE). The fulllength cDNA of prothrombinlike gene is 2 023 bp encoding a protein of 617 amino acids, with 80 bp 5′-untranslated region and a 3′-untranslated region of 89 bp including poly(A). A signal peptide between 1—15 amino acids has been detected in the predicted prothrombinlike gene. The deduced protein is highly homologous to that of mammalian and fish thrombin and shares 73% sequence identity to that of Fugu rubripes and 50%—65% sequence identity to that of various mammals. The expression of prothrombinlike gene is obviously upregulated in spleen and kidney after immunization with live attenuated vibrio. anguillarum strain, although it is also constitutively expressed in liver, gills, brain, gill and skin, suggesting that thrombin may be involved in the immune response to bacterial challenge in large yellow croaker.