Abstract: 　Objective　To analyze the clinical characteristics and CYP27B1 gene mutation vitamin D-dependent rickets type IA (VDDR-IA) in two Chinese families. Methods　Clinical manifestations, laboratory data, and radiological findings were analyzed in two patients with VDDR-IA. Nine exons and intron-exon boundaries of CYP27B1 gene were amplified by PCR and sequenced. Results　Two female patients (22 and 33 months of age, respectively) had typical manifestations, laboratory, and radiological findings of rickets. Genetic sequencing identified a homozygous mutation in exon 8 of CYP27B1 gene (1319_1325dupCCCACCC). There were more than one person with single heterozygous mutation in two families. Two patients were treated with oral calcitriol and calcium. The condition were stable and continued follow up. Conclusions　It is important to detection c.1319_1325dupCCCACCC homozygous mutation in VDDR-IA patient.