Objective　To study the clinical and genetic features of infantile malignant osteopetrosis. Methods　The clinical data and genetic testing results from one patient of infantile malignant osteopetrosis were analyzed. The related literatures were reviewed. Results　One year and six months old female, whose X-ray radiography showed generalize increased bone mineral density and reduced bone marrow space. The bone density was high in vertebral endplates and low in vertebral intermediate. Genetic testing showed that the heterozygous mutations of C.1450_1451insT c.1451A>T: 484P>P in TCIRG1 gene exon 11 in patient`s father and mother. The patient was homozygous mutation. In addition, a missense mutation c.902C>T, p. Pro301Leu of COL9A1 gene was found in the patient. Conclusion　The diagnosis of infantile malignant osteopetrosis is mainly according to clinical manifestations and genetic testing.