Objective　To explore the clinical manifestations of Tay-Sachs disease and the characteristics of HEXA gene mutation. Methods　The clinical data of Tay-Sachs disease diagnosed by gene testing in a child were retrospectively analyzed and the related literature was reviewed. Results　A 1-year-7-month-old boy mainly presented with psychomotor retardation, startle reaction and seizures. Ophthalmoscopy showed macular cherry erythema, and hexosaminidase A activity was only 0.1 nmol/(mg·h). Target sequence capture and second-generation sequencing revealed two heterozygous mutations, c.1445A>T and c.1052T>C, in the exon region of the HEXA gene in the child, causing amino acid changes p. E482V and p.L351P respectively. The results of Sanger sequencing confirmed that the two mutations were from father and mother respectively and were compound heterozygous mutation. Conclusion　Tay-Sachs disease is a rare neurodegenerative disease. Enzyme activity and genetic testing can help to clarify the diagnosis.