To detect potential mutations of chloride channel l (CLCN1) gene in a family affected with myotonia congenita.Clinical data of the proband and her parents and brother was collected. The coding regions of the CLCN1 gene were subjected to PCR and Sanger sequencing.Two missense mutations (c.937G>A and c.1205C>T), which were respectively located within exons 8 and 11 of the CLCN1 gene, were identified in the proband. The mother and father of the proband were found to harbor the c.937G>A and c.1205C>T mutation, respectively, whilst neither mutation was found in her brother.The novel missense CLCN1 mutations probably underlie the disease in this family. These have enriched the spectrum of CLCN1 mutations and may facilitate further research on this disorder.