This paper reports the effects of long-term starvation on non-specific immune parameters of Grass Carp (Ctenopharyngodon idellus). Fish with body weight (31.86±1.47)g were randomly divided into two groups (the control group and the starvation group), and three parallel samples were investigated in each experimental group. Cytotoxicity of natural killer cells against K562 in the spleen and head-kidney was detected by LDH releasing assay when the fish were starved for 15, 30, 45 or 60 d, and the activities of lysozyme in the serum and hepatopancreas and alkaline phosphatase in the serum were also examined. The results indicated that under starvation stress the natural killer activity was significantly lower in starvation group than that in control group in the kidney and spleen of the Grass Carp fingerlings(P<0.05), and the activity no longer prominently decreased as starvation time extended. The activity of lysozyme in the serum and hepatopancreas showed the trend of first-decrease then-increase with the increase of the starvation time and the activity of alkaline phosphatase in the serum was significantly lower compared to the control group on 15 d, 45 d, and 60 d, which maintained at a constant level after 30 d. All these results suggest that under long-term starvation stress the non-specific immune level of Grass Carp fingerlings decreases. Natural killer cell activity is one of the critical indexes to evaluate the cellular immunity, which is more specific and sensitive than the activity of lysozyme or alkaline phosphatase.