Sialidosis is a rare autosomal recessive disorder which is classified into type Ⅰ and Ⅱ according to the age of onset and severity of the disease.Type I,also known as mucolipidosis,is often manifested as myoclonus,ataxia,general tonic clonic seizure,and bilateral cherry-red spots in eye examination.Four cases of type Ⅰ sialidosis were reported in order to improve the diagnosis and treatment of this disease.Patients were mainly manifested as myoclonus and ataxia.Whole exon gene sequencing of the four patients all showed the mutation c.544A＞G in the NEU1 gene.Meanwhile,the new mutation c.596G＞A carried was found in case 2 and its pathogenicity was also analyzed.Finally,we summarized the clinical characteristics of type Ⅰ patients in China,noting that most patients develop all the core symptoms as the disease progresses.