This study was performed to investigate the effects of Chitosan on the nickel poisoning in rats. In the study, 150 male Sprague-Dawley were used. The experimental groups were divided into four: A (30 mg/L nickel), B (30 mg/L nickel+0.2% Chitin, Chitosan and Dithiocarbamate Chitosan), C (30 mg/L nickel+0.4% Chitin, Chitosan and Dithiocarbamate Chitosan), D (30 mg/L nickel+0.8%Chitin, Chitosan and Dithiocarbamate Chitosan). The results were as flows; 1. The nickel concentration in the livers of the control group (A) was $0.153{sim}0.186;mg/kg$ but the nickel concentration in the livers of the experimental decreased during the experimental period (P<0.05). 2. Metallothionenin levels in rat liver were $2.77{sim}3.25;ug/g$ wet,wt in control group (A), but were $2.89{sim}3.51;ug/g$ wet,wt (B), $2.97{sim}3.62;ug/g$ wet,wt (C), $2.68{sim}3.68;ug/g$ wet,wt (D). Respectively in the experimental groups. The experimental groups were inclined to increase compare to the control group (P<0.05). In conclusion, this study revealed a preventive effect of Chitin, Chitosan and Dithiocarbamate Chitosan against nickel toxicity.