Abstract The aim of this study was to explore whether there were abnormalities of CNV-like and P 300-like potentials in stressed rats following repeatedly forced swim stress. Forty male rats were randomly divided into 4 groups: the control groups (Control-1 and Control-2) and the stressed groups (Stress-1 and Stress-2). Rats in stressed groups were administered to repeatedly forced swim 7 or 14 days respectively. Body weight gain, saccharin preference test and open field test were performed. After being anesthetized with urethane, P 300-like potentials were evoked by the oddball auditory stimulation and CNV-like potentials were elicited by condition-test stimulus. Results of behavioral tests displayed less body weights and less saccharine solution intake in stressed rats and significant effects of stress on the number of crossing squares, the duration of rearing and the number of grooming in open field test. Prolonged P3 latencies and decreased P3 amplitudes of P 300-like potentials were found in the stressed rats. CNV amplitudes were lower in the stressed rats than those in control. Moreover, there were significant correlations between parameters of ERPs (including P3 latency, amplitude and CNV amplitude) and a serial of behavioral traits. This study provides an important evidence of changes of CNV-like and P 300-like potentials in depressed rats following repeatedly forced swim stress. Based on this study, ERPs should be taken into consideration and applied as the useful tools in the research work of depressed animal models.