Objective To analyze the clinical characteristics and mutation of CYP17A1 gene of a patient with 17-α hydroxylase deficiency. Methods One patient with 17-α hydroxylase deficiency was selected, and the clinical manifestations and auxiliary examinations were conducted. Besides, CYP17A1 gene detection was carried out among the patient and her parents. Results For the patient, blood pressure was higher; secondary sexual characters were underdeveloped; and serum potassium level was lower. CYP17A1 gene detection revealed a deletion of 9 bases (TCGACTCTT) on exon 8 and a homozygote mutation of D487-F489 deletion for the patient; her mother was a heterozygote carrier on CYP17A1, while no mutation was found in her father. Conclusion The 17-α hydroxylase deficiency should be considered in the diagnosis of hypertension and low serum potassium level combined with delayed sexual development. Detection of CYP17A1 gene may help to make early diagnosis.