PD-1 immunotherapy is an emerging form of cancer treatment that uses the body’s immune system to kill tumors. PD-1 is a programmed cell death molecule in Chinese, and T-cells are the body’s own immune cells that can kill cancer cells, but usually cancer cells can escape from the recognition of T-cells. This is because cancer cells have PDL-1, the programmed cell death ligand 1, which can combine with the PD-1 molecule on the surface of T cells, causing the T cells to lose their immune response to the cancer cells, which is equivalent to masquerading as normal cells. PD-1 immunotherapy is the use of immune checkpoint inhibitor drugs such as karelizumab and trepilizumab to prevent the PD-1 molecules of T cells from combining with the PDL-1 molecules of cancer cells, so that the cancer cells can’t escape from the killing of T cells to treat the cancer. It has been applied to kidney cancer, lung cancer, liver cancer, melanoma, esophageal cancer, colorectal cancer and other cancers. Immunotherapy is now more widely used in clinical application, and patients are recommended to consult and treat under the guidance of professional doctors if they feel uncomfortable.