Abstract: Objective　To analyze the screening results and mutations of phenylalanine hydroxylase (PAH) gene in children with phenylketonuria (PKU) in Tangshan. Methods　From January 2015 to December 2018, 303 777 newborns in Tangshan were selected to detect the content of phenylalanine (PA) in the heel blood by ninhydrin fluorescence method. The polymerase chain reaction (PCR) and gene sequencing methods were used to detect the PAH gene in PKU children. Results　A total of 609 suspected positive cases were found in the preliminary screening of 303 777 newborns. Among them, 411 cases were recalled for re-examination. The recall rate was 67.49%, 42 newborns were diagnosed, and the incidence rate was 13.8/100 000. The PAH gene sequencing in 42 PKU patients showed that 62 mutations were detected on 84 chromosomes, and the detection rate was 73.81%. Twelve mutations were detected, including 8 missense mutations, 2 nonsense mutations, 1 deletion mutation, and 1 splice mutation. The PAH gene mutations of patients were distributed in exons 2, 3, 6, 7, and 9, with the most exon 7 (35, 56.45%), followed by the third exon (14, 22.58%). The most common mutant genes were Exon7-R243Q (18, 29.03%), Exon3-R111X (10, 16.13%) and Exon7-R261Q (10, 16.13%). One child with typical PKU was found in the screening. Two heterozygous mutations were simultaneously found in the exon region: c.208-210delTCT (deletion mutation) and c.964G>A (guanine>adenine). Conclusion　The incidence of neonatal PKU is slightly higher in Tangshan than that in the whole country. The PAH gene mutations are mainly missense mutations. Exon 7 is the high-frequency mutation site of PAH gene in children in Tangshan.