PKU, also known as phenylketonuria, is an autosomal recessive disorder caused by an enzyme defect in the phenylalanine metabolic pathway, resulting in the failure to convert phenylalanine to tyrosine, which eventually leads to the accumulation of phenylalanine and pyruvate and its massive excretion in the urine. After 3-4 months of age, the child may gradually develop backward intellectual and motor development, the whole body and urine emit a special smell of rat urine, often accompanied by eczema, microcephaly, increased muscle tone, white skin, lighter hair and iris color, abnormal behavior, tremor, etc. Some children may behave normally or only see slightly low intelligence, different degrees of white skin, in general, the newborn can do the urine iron trichloride test, the screening of dinitrophenyl hydrazine test at birth. To confirm the diagnosis of PKU, the blood phenylalanine concentration should be greater than 1.22 mmol/L and the blood tyrosine should be normal or low. The main treatment for PKU is the use of low-phenylalanine foods, for example, small infants can be fed low-phenylalanine formula, and when supplementary foods need to be added they should also be vegetables, fruits, starches and other foods that contain less protein. The earlier the diet is started, the better the treatment effect. The low-phenylalanine diet should be adhered to at least 10 years of age, and can be extended to adolescence if possible, and if female patients intend to have children in the future, the diet should be adhered to until after childbearing age. Drug therapy mainly uses levodopa, pentoxifylline, tetrahydrobiopterin, etc. Different drugs can be used according to the symptoms.