According to WHO Manual of Laboratory Tests for Human Semen (5th edition), the reference value of normal semen is total sperm count >39×106 per ejaculation, and the normal minimum value of sperm density is ≥15×106/ml. oligozoospermia can be diagnosed by routine semen analysis for more than 3 times, and the sperm density is <15×106/ml or the total number of sperm counts is <39×106 per ejaculation. Sperm density <15×106/ml is mild oligospermia, sperm density <10×106/ml is moderate oligospermia, and sperm density <5×106/ml is severe oligospermia. Artificial insemination (AI) refers to the injection of washed and processed male semen into the female reproductive tract by non-coital artificial means in order to fertilize the egg and sperm naturally for the purpose of pregnancy. Intrauterine insemination (IUI) is used in our center. Semen processing is mainly aimed at increasing the density of sperm with high motility, removing prostaglandins, inflammatory cells, anti-sperm antibodies, bacteria, and debris from seminal plasma to promote sperm capacitation and improve fertilization. And injecting semen directly into the uterine cavity avoids the loss of sperm in the vagina and cervix. Since artificial insemination is still natural fertilization in the body, it requires the woman to have at least one side of the fallopian tube open and a dominant follicle to be discharged by natural monitoring or ovulation promotion. For mild oligozoospermia, IUI with sperm washing enriches high quality sperm and reduces sperm loss in the female reproductive tract, improving the chances of conception. For patients with moderate to severe oligozoospermia, the number and density of sperms after sperm washing may still not meet the requirements of natural fertilization, or patients who have not yet conceived after 2-3 times of artificial insemination, we recommend IVF (In Vitro Fertilization - Embryo Transfer), which is also commonly known as IVF (In Vitro Fertilization).