Male SD rats were randomly divided into normal control group and cigarette smoke group (CS group). Rats in CS group were exposed to cigarette smoke in ventilated smoking chambers and divided into low-dose group (about 2.5 cigarettes, exposed for 10 minutes a day), medium-dose group (about 5 cigarettes, exposed for 20 minutes a day) and high-dose group (about 10 cigarettes, exposed for 40 minutes a day). The influence of cigarette smoke exposure on learning and memory function of rats, on pathological changes of hippocampus and on the expression of brain-derived neurotrophicfactor (BDNF) was explored by Morris water maze, H-E staining and immunohistochemistry staining, respectively. The results showed that the escape latency of CS group was significantly decreased and the expression of BDNF was significantly increased compared to normal control group 30 d after exposure; the escape latency of medium-dose group was shorter than that of the normal control group and the expression of BDNF of CS group was significantly increased 60 d after exposure; the escape latency of CS group was significantly increased and the expression of BDNF was significantly increased compared to normal control group 180 d after exposure. The hippocampus of rats in each group showed no significant change in H-E staining. The results showed that the function of learning and memory of rats was increased after short-term cigarette smoke exposure but decreased gradually with increased exposure time. This effect was closely related to the expression of BDNF in hippocampus.