Objective To analyze the clinical features of myotonic dystrophy (DM) and to improve the understanding and diagnosis of DM.Methods The clinical data of 21 patients with DM were retrospectively summarized to analyze the clinical manifestations and the results of electromyography/electroneurography, pathological examination, laboratory testing, imaging examination, and genetic testing.Results All patients had insidious onset of disease, with hand weakness and stiffness as initial symptoms. Five cases had a family history. Damages of the heart, eyes, endocrine system, central nervous system, and other systems were found in some cases. Electromyography in 19 cases revealed myopathic changes in all of them and myotonic potentials in 16 of them. Muscle biopsy in 10 cases disclosed atrophy of some muscle fibers, degeneration and necrosis of muscle fibers, centrally placed nuclei and formation of sarcoplasmic mass, and accumulation of amorphous cytoplasmic bodies in some atrophic muscle fibers. One case had an increased copy number of CTG repeats in myotonic dystrophy protein kinase(DMPK) gene.Conclusions The main clinical manifestations of DM include progressive myotonia, muscle weakness, and myotrophy, as well as multisystem damages. Comprehensive clinical evaluation combined with electromyography/electroneurography and pathological examination would be helpful for the understanding of DM. Genetic testing, which is valuable for the confirmed diagnosis of DM, can be performed if possible.