Adiponectin (APN) is an important cytokine secreted by fat cells that is responsible for regulating numerous biological functions. However， the APN gene in lamprey and its precise function remain unidentified. In this study， the full-length cDNA sequence of L-APN was cloned， and it encoded a protein of 267 amino acid residues with a globular domain. The results of immunohistochemistry and FACS assays showed that APN protein was distributed in multiple tissues. L-APN expression in the supraneural body (SB) and leukocytes was differentially upregulated in response to Gram-negative bacteria， Gram-positive bacteria and poly (I:C). The expression levels of inflammatory cytokines were upregulated， and a proapoptotic effect was stimulated in SB cells treated with recombinant APN. Furthermore， L-APN could inhibit cell proliferation and arrest cell growth in the G1 phase. In summary， the APN protein from the lamprey plays an important role in inhibiting cell proliferation， inducing the production of inflammatory cytokines and promoting cell apoptosis， and it is also involved in immune responses and immune defenses. Our data provide insights into the evolutionary origin of the structure and function of APN gene.