The invention discloses a kit for detecting a PAH (phenylalanine hydroxylase) gene of phenylketonuria. The kit comprises (1) a gene chip with 13 mutation sites of the PAH gene and a normal control complementary nucleotide sequence probe thereof and (2) various primers for amplifying DNA sequences in clinical samples, wherein the probe is SEQ ID Nos: 1-26 or the sequence complementary to SEQ ID Nos: 1-26; the DNA sequences of the primers are SEQ ID Nos: 27-40. By virtue of the kit for detecting the PAH gene, which is disclosed by the invention, a joint detection platform for detecting 13 common mutation sites of the PAH gene is provided, a synchronous joint detection is achieved, the specificity of the detection is improved, the cost is reduced and the detection time is shortened; the kit is of great significance for screening phenylketonuria-infected patients and carrying out genetic counseling and prenatal diagnosis.