Objective To investigate whether there is correlation exists in the effection of chronic unpredictable stress on active avoidance behavior and electroencephalogram ( EEG) of rat. Methods Twenty male SD rats (weight～200 g) were randomly divided into control group( n= 10) and model group( n- 10). Rats in model group were subjected to chronic unpredictable stress . Active avoidance response were observed with GeminiTM avoid system and EEG power spectrum was evaluated with Powerlab system. Results The failure rate in active avoidance test was correlation with delta wave power in EEG. Compared with control group, rats in model group had reduced failure rate in active avoidance task(42 ±36)% vs (82 ±30)% , P＜0.05). The EEG power spectrum of model group rats increased in delta band((47.09 ±22.86)μV2 vs (22. 55 ± 11. 57) μV2, P＜0. 05), which had the significant difference between the two group rats. The failure rate of active avoidance task in model group rats was positive correlation with EEG power spectrum of delta wave (r = 0. 717, P ＜ 0. 05) . Conclusion Chronic unpredictable stress facilitated active avoid behavior and changed spontaneous EEG, which suggested chronic unpredictable stress actived the neurotransmitter network system involved with active avoidance task in central nervous system. Brain cognitive function correlated positively with brain electrophysiology activity measured in chronic unpredictable stress induced rat model.