Objective To explore the morbidity and the related clinical factors of hepatic dysfunction in children with hyperthyroidism. Methods Totally 393 children with hyperthyroidism were divided into 2 groups: hyperthyroidism with hepatic dysfunction group(174 cases) and hyperthyroidism with normal liver function group(219 cases). The gender, age, family history of thyroid disease, duration of disease, liver function and thyroid function indicators were retrospectively analyzed in the 2 groups. Results The morbidity of hepatic dysfunction in children with hyperthyroidism was 44.3%(174/393 cases), and the most common abnormal hepatic function parameter was the increase of alanine aminotransferase(ALT), which accounted for 88.5%(147 cases). There were no significant differences of gender, age, family history of thyroid disease, duration of the disease, or levels of thyroid peroxidase antibodies and thyroglobulin antibodies between the hepatic dysfunction abnormal group and liver function normal group(all P>0.05). Free triiodothyronine and free thyroxine of hepatic dysfunction abnormal group were significantly higher than those in liver function normal group(Z=-7.90, P=0.000; Z=-8.80, P=0.000); and thyroid stimulating hormone of hepatic dysfunction abnormal group was significantly lower than that in liver function normal group(Z=-4.60, P=0.000). Liver functions after treatment with Methimazole of the hyperthyroidism cases were all significantly improved: ALT(Z=-14.90, P=0.000), aspartate aminotransferase(Z=-5.30, P=0.000), γ-glutamyltransferse(Z=-5.50, P=0.000), alkaline phosphatase(Z=-5.90, P=0.000), total bilirubin(Z=-5.50, P=0.000), direct bilirubin(Z=-4.60, P=0.000), indirect bilirubin(Z=-4.60, P=0.000). Conclusions Hepatic dysfunction caused by hyperthyroidism in children is common and correlated with thyroid function.Elevation of ALT is the most common abnormal hepatic function parameter.The hepatic dysfunction is usually transient and mild and is to be normal with normalized thyroid function. Key words: Child; Hyperthyroidism; Hepatic dysfunction; Thyroid function