Abstract: Objective　To explore the clinical phenotype and genotype characteristics of infantile polycystic kidney. Method　The clinical data of polycystic kidney disease in one infant were retrospectively analyzed, and the correlation between clinical phenotype and genotype was analyzed. Results　In this infant the polycystic kidney was discoved in the fetal period, and shortness of breath, foaming at the mouth were present after birth. Abdominal magnetic resonance imaging indicated that there was medullary sponge kidney in both kidneys accompanied by mild effusion and cysts were found in the right kidney. Gene detection showed a missense mutation c.1123 C>T (Arg375Trp) of exon15 in PKHD1 gene. The exon31 of PKHD1 gene had a missense mutation c.3617G>T (Gly1206Val), which was a new missense mutation. The exon18 of PKD1 gene had a missense mutation c.7211G>A (Arg2404Gln), which is a complex heterozygous mutant of homozygote.  All of the mutations are  missense mutations. The infant was improved and discharged after treatment, and renal function was normal during 4 months of follow-up. Conclusion　Gene detection can be used for early diagnosis of infantile polycystic kidney disease. Newborns with two missense mutations can survive, and exon31 mutation c.3617G>T (Gly1206Val) is a new finding.