Objective 　To investigate the features of clinical symptoms and pathological changes of mitochondrial encephalomyopathy. Methods　16 cases of mitochondrial encephalomyopathies were analyzed on clinical features, histochemical changes and ultrastructure observations of muscles.Results　The average proportion of RRFs was 5.9% in 16 cases and central nuclears were present in 11 cases. There were blue fibers on SDH/CCO double stain sections in 12 out of 13 cases. The distribution of blue fibers was concordent with that of RRFs. There were crystal include body in mitochondria of 4 cases. Conclusions　The diagnosis of mitochondrial encephalomyopathy could be made accoding to the presence of blue fibers on SDH/CCO double stain sections and the mitochondria encephalomyopathy could be distinguished from other myopathies.