Objective To investigate the change of event-related potential P300 and its effect on cognitive function in patients with positive non-invasive transcranial Doppler (TCD) foaming test in stroke.Methods A total of 138 stroke patients who received TCD foaming test in Shenyang 242 Hospital from January to December 2019 were selected as the study subjects.Sixty-nine normal patients with negative TCD foaming test were set as the control group,and 69 patients with positive TCD foaming test were set as the observation group.The P300 amplitude,P300 latency,cognitive function and the incidence of migraine were compared and analyzed between the two groups.Results There was no significant difference in P300 amplitude between the two groups (P＞0.05).The latency of P300 in the observation group was longer than that in the control group,the difference was statistically significant (P＜0.05).The proportion of combined cognitive dysfunction in the observation group (18.84%) was higher than that in the control group (5.80%),the difference was statistically significant (P＜0.05).The incidence of migraine in the observation group (69.57%) was higher than that in the control group (26.09%),the difference was statistically significant (P＜0.05).Conclusion Positive TCD foaming test has certain influence on cognitive function of stroke patients,and the prolongation of P300 latency is related to right to left shunt.