Tumor is the main lethal type of major diseases that human beings are facing nowadays. Traditional therapies, such as chemotherapy, surgery, radiotherapy, etc, have been the mainstay of tumor treatment for a long time, and still have their own limitations in terms of effectiveness. In recent years, immunotherapy for tumors has attracted much attention with the rise of strategies such as immune checkpoint inhibitors, chimeric antigen receptor T-cell (CAR-T) relay therapy, and anti-tumor vaccines. Among them, CAR-T cell therapy, as a breakthrough tumor immunotherapy method, can precisely target tumors at the cellular and molecular levels by modifying the patient’s own T cells to express recombinant antigen receptors targeting specific tumor antigens, breaking the restriction of the major histocompatibility complex (MHC) of the natural T cells themselves. It can precisely target tumors at the cellular and molecular levels, and thus can efficiently and specifically identify and kill cancer cells, providing a new perspective for treatment. Since the approval of the first CAR-T therapy by the US Food and Drug Administration (FDA) in 2017, in addition to still maintaining significant advantages in the field of classical multiple hematologic malignancies, it has also made outstanding progress in the treatment and clinical trials of some solid tumors and autoimmune diseases, among others. This paper  will briefly review the current principles, applications, challenges and directions of development of CAR-T technology.