Abstract: To reveal the role of TNF-α receptor genes TNF-R1 and TNF-R2 in the Nile tilapis（Oreochromis niloticus）immune processes，we cloned the full-length cDNA sequences of TNF-R1 and TNFR2 from Nile tilapia by RACE. Sequence analysis showed that the full length of TNF-R1 cDNA was 2 275 bp，containing an open reading frame of 1 335 bp，and encoding a protein with 444 amino acids；the full length of TNF-R2 cDNA was 1 719 bp，containing an open reading frame of 1 476 bp，and encoding a protein with 491 amino acids. Protein structure prediction showed that TNF-R1 have three cysteinerich domains and an intracellular death domain，while TNF-R2 have four cysteine-rich domains and without death domain. Systematic evolutionary analysis showed that the tilapia TNF-R1 and TNF-R2 were highly homologous with those of other vertebrates. Phylogenetic tree showed that TNF-R1and TNF-R2 were clustered separately. By qRT-PCR，the highest expression levels of TNF-R1 and TNF-R2 mRNA were found in the gill，head kidney and spleen，and the lowest levels were in pituitary and muscle. The expression of TNF-α，TNF-R1 and TNF-R2 genes can be increased to varying degrees by stimulating the tilapia kidneys and spleen white cells incubated with LPS and Poly Ⅰ：C，respectively. The expressions of three genes in the head，kidney and spleen can be increased after intra-peritoneal injection of Streptococcus agalactiae. This study has some reference value to show the immune regulation mechanisms of TNF-R1and TNF-R2 to improve the level of healthy breeding of tilapia.

Key words: TNF-α, TNF-R1, TNF-R2, Oreochromis niloticus, immunity, Streptococcus agalactiae