The blood type of a child is determined by both the father and the mother. The child’s blood type may be the same as the mother or (and) the father, or it may be different from both parents. The blood type is usually the type of specific antigen on the surface of the red blood cell membrane in the blood, and is mainly classified into ABO blood group system and Rh blood group system. The blood type of a child is not only determined by the father or mother alone, but is controlled by the expression of blood group genes on both chromosomes. According to the ABO blood group system, blood types are classified as A, B, AB and O. The inheritance of the human blood group system is controlled by three genes on the chromosomes, A, B and O. Only two of the three genes can be expressed on a pair of chromosomes, one from each parent to the child. The three genes can be expressed in six forms, namely AO, BO, AB, AA, BB and OO, of which A and B genes are dominant genes and O genes are recessive genes, of which the recessive genes in AO and BO will not be expressed, so there are only four expressions of blood type, namely AB, A, B and O. If one parent is AB and one parent is O, the child’s blood type may be A or B. If both parents are A or B, the child may also be O. At this time, the blood type is different from both parents and can be considered as neither following the father nor the mother. If both parents are type O, the child should also be type O. The genotype of the same person is not necessarily the same, the blood type is determined by heredity, and the blood type of a normal person remains unchanged for life; the inheritance of the Rh blood group system is also determined by both parents, the positive is the dominant gene, the negative is the recessive gene, if both parents are Rh negative, the child will be the same, and the Rh blood group system has greater significance in clinical application.