Blood after coitus may be due to torn ligament, foreskin injury and blood clotting dysfunction. 1. Torn ligament: this situation is common in men’s first coitus, due to lack of skill and excessive excitement, improper posture or excessive force during coitus, resulting in torn ligament, may appear after coitus with blood. 2. Tear of foreskin: If the man is suffering from prepuce, during coitus, due to the narrow opening of the foreskin, the foreskin can not be upturned, with the action of coitus, the foreskin will gradually move up, which can lead to injury to the foreskin, thus causing bleeding. 3. Coagulation dysfunction: If you suffer from hemophilia, leukemia and other blood system diseases, the male body coagulation dysfunction, when the coitus is too intense, a little carelessness will cause bleeding. If men have blood after intercourse, they should go to regular hospitals in time to find out the cause of the disease, and choose a suitable method of treatment under the guidance of professional doctors.