Objective To analyze the diagnosis and treatment of hereditary hypomagnesemia. Methods The clinical data of hereditary hypomagnesemia of one child were retrospectively analyzed and the related literatures were reviewed. Results The boy was admitted at 6 months of age due to convulsion caused by hypomagnesemia, and the blood magnesium level was only maintained at about 0 . 6 mmol/L after magnesium supplementation. Whole exome sequencing showed that there were compound heterozygous variations, c. 2495 A>G (p.Tyr 832 Cys) and c. 3357 C>A (p. Cys 1119* ), in TRPM 6 gene. The child was treated with oral magnesium for a long period of time and grew up l during follow-up. Conclusions Compound heterozygous variation in TRPM 6 gene (c. 2495 A>G and c. 3357 C>A) was responsible for hereditary hypomagnesemia 1 (intestinal). Diagnose and treatment for patients in time may avoid irreversible neurocognitive impairment.