To investigate effects of yam on growth performance and immunity function of rainbow trout(Oncorhynchus mykiss),four test groups were used,which consisted of basic feed group(control),0.1%,0.2% and 0.4% yam extract addition groups. Rainbow trout were randomly allotted to four groups and were fed for 56 d.The results were as follows:compared with the control group,0.1%,0.2% and 0.4% yam extract had no significant effect on the growth performance,but significantly decreased the content of blood urea nitrogen(BUN) and the inhibitory effects were 51.20%,64.06% and 49.80%,respectively,while significantly increased complement 4(C4) level(the induction effects were 154.35%,144.03% and 304.68%,respectively)and lysozyme(LZM) activities(the induction effects were 42.41%,34.95%and 27.89%,respectively) in the serum of rainbow trout;total protein(TP),interleukin-6 (IL-6),tumor necrosis factor α(TNF-α), and superoxide dismutase(SOD) levels were significantly increased in the serum of 0.2% and 0.4% groups(the induction effects were 36.49% and 45.97%,45.01% and 56.25%,247.32% and 414.15%,82.14% and 110.71%,respectively),while alkaline phosphatase(ALP) activities in 0.2% and 0.4% groups,glutamic-pyruvic transaminase(GPT) activities in 0.1% and 0.2%groups,CREA content in 0.1% group were significantly decreased(the inhibitory effects were 51.60% and 56.75%,77.37% and 60.71%,41.96%,respectively);interleukin-2(IL-2)content in 0.2% group,albumin(ALB)content and acid phosphatase(ACP) activity in 0.4% group were significantly increased(the induction effects were 87.59%,30.73% and 63.77%,respectively).The above results showed that the growth performance of rainbow trout could not be affected by adding the extracts of yam to the basic feed,while the non-specific immune function could be improved.The recommended dosage was 0.2%—0.4%.