The causes of post-coital bleeding include vaginitis, cervical cancer and columnar epithelial ectasia of the cervix. 1. Vaginitis: patients with bacterial, mycobacterial or trichomonas vaginitis may suffer from congestion and edema of local mucosa due to inflammation, leading to bleeding after sexual intercourse. 2. Cervical cancer: patients with cervical cancer may suffer from post-coital bleeding due to abundant blood vessels on the surface of the tumor and high brittleness, etc. Post-coital bleeding is also the reason for many patients with early stage of cervical cancer to consult the doctor. 3. Columnar epithelial ectasia of the cervix: once known as cervical erosion, bleeding after intercourse can also occur, which may be caused by frequent friction during intercourse. There are many other reasons for post-coital bleeding. It is recommended that such patients go to regular hospitals, cooperate with doctors to complete relevant examinations, identify the causes and deal with them positively.