The retention of semen samples plays a decisive role in the accuracy of the experimental diagnosis of infertility. Correctly instructing the subject to collect semen is the most important and basic work in the experimental diagnosis of male infertility. Specific details are as follows: 1. Abstinence must be 2-7 days before semen examination (i.e. no more ejaculation within 2-7 days after the last semen discharge, the semen specimen within this period is suitable for semen examination). Abstinence for too short a period (<2 days) or too long (>7 days) is not suitable for semen examination. If the abstinence period has exceeded 7 days, the semen should be discharged within 2-7 days and then come back for semen examination. 2. It is required that semen be collected by masturbation and semen should not be retained by condom or interrupted sexual intercourse. When semen is collected, special attention should be paid to the ejaculation process which should be thorough, i.e. try to make the semen in the body ejaculate completely. Insufficient ejaculation (insufficient sexual excitement) will result in a smaller volume of semen than the actual semen volume. If the semen volume is not close to the real level of the detector, it will seriously affect the accuracy of the test results. 3. Semen specimens should be collected completely in the designated container and no semen should be left out. Otherwise, the accuracy of the test results will be affected. 4. Semen collection should preferably be performed in the hospital, and semen should be sent for testing immediately after ejaculation. If semen is left outside the hospital, care should be taken not to contaminate the semen, and the exact time of semen ejaculation should be recorded on the laboratory sheet immediately after semen removal. The semen specimen should preferably be delivered within 30 minutes, and the maximum time should not exceed one hour. When it is cold, semen specimens should be kept warm (20~37℃) during transportation. 5. The container used for semen collection is highly clean and should not contaminate the inner wall of the container.