ICSI, or intracytoplasmic single sperm injection, is a second generation “in vitro fertilization” technique in which a single sperm is injected into the egg to fertilize it with the help of a microscopic operating system. This technique requires only a few sperm to achieve fertilization and pregnancy, and is the most effective treatment for patients with severe male factor infertility. Its indications are: 1. Patients with oligospermia or weak spermatozoa. 2, unexplained infertility: the fertilization rate of second-generation IVF technology is higher than that of conventional IVF, and ICSI technology can be recommended for patients with unexplained infertility. 3.Patients who have failed in previous IVF fertilization: Evidence shows that the fertilization rate of patients who have failed in previous IVF fertilization will not exceed 25%. The second generation of IVF technology can be used to achieve a higher success rate. 4. Garden-head (acrosome deficient) sperm or completely inactive sperm: the second generation IVF technique is the only way to treat them. 5. Obstructive or non-obstructive azoospermia: sperm with low numbers or poor motility obtained through epididymal or testicular surgery can be treated with second-generation IVF technology. 6.Sperm retrieval difficulties or inability to ejaculate after egg retrieval: semen can be collected and stored for freezing. If there is no spare sperm in an emergency, ICSI can be performed on epididymal or testicular sperm as a remedial measure. 7. Pre-implantation genetic diagnosis: For embryos that need to be diagnosed, it is necessary to use the second generation of IVF technology in order to avoid the influence of sperm adhering to the transparent strip on the test results. ICSI plus IVF is the most effective treatment for male infertility, with a live birth rate of 20-25%.