The immune system is like a well-trained elite force that defends the health of the body at all times. In general, this force has three functions: one is to defend against infections, the second is to identify itself, remove foreigners and maintain stability, and the third is immune surveillance to prevent loss of control. Once this force in that aspect of the problem, each other can not coordinate cooperation echo, the immune system is out of balance and chaos, the three major functions of the immune system is weakened or abnormal, resulting in the body to develop primary immunodeficiency disease. Primary immunodeficiency diseases are defined as defects in immunoreactive cells such as T cells, B cells and macrophages and/or complement and cellular immunoreactive molecules, and impaired immune response, causing the body to be susceptible to recurrent and severe infections, along with abnormalities in self-stabilization and immune surveillance functions, making the body more likely to develop autoimmune diseases, allergic diseases and malignancies. Most of these diseases are due to congenital underdevelopment of organs, cells, molecules and other components of the immune system, including specific and non-specific immunodeficiencies, and often develop in infancy or childhood. The etiology of most primary immunodeficiency diseases is not well understood, but their clinical manifestations are diverse and therefore considered to be multifactorial. In particular, genetic factors play a role in most of these disorders; some have identified chromosomal loci for defective genes; some are associated with the in utero environment, such as maternal infection with rubella virus and cytomegalovirus, and some are also associated with alcoholism or drug use. The immune system can be divided into non-specific and specific immunity. The components of non-specific immunity are mainly phagocytes, complement and cytokines, while the components of specific immunogens are mainly T cells, B cells and immunoglobulins. Therefore, according to the above composition of the immune system, primary immunodeficiency diseases are usually divided into four categories: a. Antibody deficiency diseases, the cause of which is the developmental disorder, reduced number or lack of B lymphocytes, resulting in the lack or reduction of antibodies (immunoglobulins), is the highest incidence of primary immunodeficiency diseases, accounting for more than 50%. The most common ones are congenital absence of gammaglobulinemia, common variant immunodeficiency, infantile temporary hypogammaglobulinemia, and selective IgA deficiency. Second, cellular immunodeficiency, with thymic hypoplasia being more common. It is caused by impaired development of the 3rd-4th pharyngeal sac at about 12 weeks of gestation. Most children with hypoparathyroidism often have postnatal hypocalcemic convulsions that are not easily corrected. The child has a peculiar facial appearance and may have congenital heart disease and esophageal atresia; the thymus shadow is not visible on X-ray and the total number of lymphocytes, especially T-lymphocytes, is low on blood tests. The children often have recurrent infections and they are the main contraindication for planned immunization with live attenuated vaccines because their immunity is really low and live attenuated vaccines can cause fatal infections. Graft-versus-host reactions are likely to occur after transfusion of whole blood or plasma or after allogeneic bone marrow transplantation. The children are stunted in growth and development and often die prematurely in childhood. Combined immunodeficiency, in which both cellular and humoral immune functions are defective. This includes severe combined immunodeficiency, which is severe and often results in death in infancy. Patients with combined immunodeficiency with thrombocytopenia and eczema (WAS syndrome) are mostly killed by infection and bleeding. Fourth, primary nonspecific immunodeficiencies, including primary complement defects and phagocyte-deficient diseases, account for about 10% of primary immunodeficiency diseases. To date, more than 100 primary immunodeficiency diseases have been identified, each of which has a characteristic presentation and occurs for different reasons.