Abstract: To study the toxicity of nicotine at addictive dosage using rats as a model, SD rats were injected with nicotine subcutaneously, meanwhile the nicotine-dependence model of rat was established by using CPP apparatus, and the variation of initial nicotine-dependence duration was investigated successively. The blood count parameters, blood biochemistry and histopathology of each organ of nicotine-dependent rat were studied. The results showed that:1) 0.2 mg/kg nicotine induced stable nicotine-dependence in rats after five dosing periods, and the degree of nicotine dependence increased first and then decreased to the level at the initial stage of addiction. 2) The results of blood count parameters and blood biochemistry indicated that nicotine down-regulated the expression of inflammatory index EOS and up-regulated the levels of liver damage-related GGT and TBIL. 3) Histopathology results indicated that nicotine caused mild edema of liver and kidney in rats, the distinct pathological damage of lung was mainly inflammatory injury. Therefore, nicotine had mild toxicity for rats at nicotine-dependence dosage (0.2 mg/kg), the lung, liver and immune system of rats suffered different degrees of toxic damage due to nicotine.