Objective: To study the effect of chronic stress on spatial learning and memory and nitric oxide (NO) in hippocampus of the rats Method: Chronic stress model was established by electric-foot accompanied with noise Morris watermaze was used to observe spatial learning and memory abilities, contents of NO and activities of NOS in hippocampus were measured during the test Result: The spatial learning and memory of chronic stress rats were significantly decreased in Morris watermaze Contents of NO (3 87?0 47 nmol/mgpro) and NOS activity (102 64?13 33 pmol/mgpro/min) in hippocampus of the stress rats were significantly higher than that of normal rats (2 76?0 43 nmol/mgpro, 78 25?10 67 pmol/mgpro/min respectively) Conclusion: Chronic stress impairs spatial learning and memory abilities of rats, which may be related to the increase of NO in their hippocampus