The common causes of low semen are as follows: 1, the short time between sexual intervals, so that the amount of semen may be reduced; 2, there is a long-term decrease in the amount of semen, generally common reasons may be physical problems, refers to the poor physical condition; 3, some patients may be mental and psychological pressure caused by the reduction of semen; 4, disease caused by the reduction of semen, such as retrograde ejaculation during sex, etc.. If there are no abnormal physical symptoms, you can observe temporarily. It is recommended to pay attention to diet and nutrition in general and do physical exercise in moderation.