Objective To explore the effects of low-frequency repetitive transcranial magnetic stimulation（ rTMS） on cognitive of patients with post-stroke memory disorders（ PSMD） and the event-related potential P300. Methods A total of 50 patients with PSMD， who were hospitalized in the rehabilitation department of Xuzhou Central Hospital from September 2019 to June 2020， were prospectively and continuously enrolled， and divided into stimulation group and sham stimulation group with 25 cases each by random number table method. Both groups were given drugs and routine rehabilitation training. The stimulation group was given low-frequency（ 1 Hz） rTMS treatment， and the sham stimulation group was given sham rTMS treatment for 4 weeks. Before and after treatment， evaluations were performed on the Mini Mental State Assessment Scale（ MMSE）， Montreal Cognitive Assessment Scale（ MoCA）， Rivermead Behavioral Memory Scale（ RBMT- Ⅱ）， Modified Barthel Index（ MBI） and P300. Comparison of treatment was made between different groups. Rusults There was no statistically significant difference in MMSE， MoCA， RBMT-Ⅱ and MBI between the two groups before treatment（ all P＞0.05）. After 4 weeks treatment， the scores in stimulation group［ MMSE score （21.52±4.51）， MOCA score（ 16.80±3.88）， RBMT-Ⅱ score（ 17.28±3.30）， MBI score（ 64.60±14.21）， P300 latency period（ 346.04±40.25） ms， amplitude（ 10.76±3.44） μV］ were better than those in sham stimulation group［ MMSE score（ 18.28±4.56）， MOCA score（ 13.92±4.58）， RBMT- Ⅱ score（ 14.52±3.81）， MBI score （52.80±13.93）， P300 latency period（ 383.39±51.23） ms， and amplitude（ 7.28±3.00） μV］. Before and after treatment， the differences of scales results and P300 parameter of the simulation group were all better than those of the sham simulation group［ MMSE score（ 4.68±1.63） vs.（ 2.40±1.61）， MOCA score（ 4.82±1.56） vs. （1.82±1.33）， RBMT-Ⅱ score（ 5.04±1.21） vs（. 2.44±1.85）， MBI score（ 21.80±7.62） vs（. 13.20±6.60）， P300 latency period -45.52（-121.69，-0.67） ms vs. -21.10（-60.61，29.31）ms， and amplitude 5.36（2.08，8.21） μV vs. 1.18（0.12，2.08） μV； all P＜ 0.05］. Conclusions Low-frequency rTMS can improve memory function of PSMD patients， and is more helpful to recovery of daily living ability. P300 can objectively reflect the effect of low-frequency rTMS more on improving memory function.