Abstract: Toll receptors are important pattern recognition receptors(PRRs) and play a vital role in the immune system of invertebrates.This paper investigates a new type of Toll receptor from Penaeus monodon (PmToll9).By constructing an in vitro cellular immune model in HEK293T cells, we found that PmToll9 could express a recombinant eukaryotic protein in HEK293T cells successfully with western blot technology.The dual-luciferase reporter system shows that PmToll9 could activate NF-κB reporter gene significantly when it was transfected with 200 ng DNA in HEK293T cells.The qRT-PCR data reaveal that PmToll9 can activate TLR signaling pathway of HEK293T cells and promote high expression level of the downstream factors(MyD88, TNF-α and IL-10).Meanwhile, ELISA results confirm that PmToll9 could increase TNF-α protein level. The in vivo bacteria stimulation in P.mondon shows that Streptococcus agalactiae could activate the mRNA expression of PmToll9 in hepatopancreas, intestine, lymph and gill, while Vibrio harveyi could inhibit the mRNA expression of PmToll9 in hepatopancreas.It is revealed that PmToll9 could be activated and inhibited by S.agalactiae and V.harveyi via Toll signaling pathway to induce the immune defenses, respectively.