Objective　To explore the clinical characteristics, diagnosis, and treatment of primary hyperoxaluria type Ⅰ (PHⅠ). Method　The clinical manifestations and laboratory examination results of PHⅠ in 2 children were retrospectively analyzed, and whole exon sequencing was performed in family members. Results　The ages at onset of the 2 children were 2 months and 1 year and 5 months respectively. Both had renal failure, accompanied by different degrees of anemia and nephrolithiasis. The homozygous variant of c.815_816GA was found in a child and the compound heterozygous variants of c.25_26 insC and c.815_816 insGA were found in another child in AGXT gene by whole exon sequencing. Kidney replacement combined with symptomatic treatment was performed after diagnosis of PHⅠ. Conclusion　PHⅠ has no specific clinical manifestations, and renal failure is developed rapidly in some children.