Abstract: Head kidney leucocytes of malabar grouper Epinephelus malabaricus were cultured in Angelica sinensis polysaccharides(ASP)in vitro for 3,6,12,24 and 48 h,and changes in mRNA levels of Toll-like receptor 22 (TLR22)pathway-related genes were analyzed by quantitative real-time PCR to investigate effects of ASP on the expression of TLR22 signal pathway-related genes in malabar grouper.The results showed that mRNA levels of TLR22 and TIR-domain-containing adaptor inducing interferon-β(TRIF)were up-regulated gradually with time, with the maximum TLR22 value in 24 h and the maximum TRIF value in 12 h.The peak expression of downstream transcription factor IRF3(interferon regulatory factor 3)was observed in 24 h,and the peak expression of major histocompatibility complex(MHC)and tumor necrosis factor-α(TNF-α)genes was found in 24 h.The maximal expression of interferon-8(IL-8)mRNA appeared in 48 h.These findings indicate that ASP leads to activate TLR22 and its downstream genes which play an important role in malabar grouper immune regulation.