Mitochondrial diseases refer to a group of multi-system diseases caused by dysfunction of mitochondrial respiratory chain leading to ATP synthesis disorder, can affect muscles, central nervous system, kidneys, cardiovascular, eye, ear, digestive, endocrine, cardiovascular and renal systems individually or simultaneously. It can occur in any part of the body or at any age, the incidence is about 1/8500. For this test, CapitalBio use two long-segment PCR amplification and high-throughput sequencing technologies to analyze the full length of the entire mitochondrial gene (16569bp), the latest Cambridge version of the mitochondrial genome NC_012920 was used as a reference for comparison and analysis.