Objective To explore the clinical characteristics and prognosis of hypertrophic cardiomyopathy (HCM) with left ventricular enlargement in children. Methods The clinical data of HCM children hospitalized from July 2008 to March 2020 were retrospectively analyzed, and the followed-up was conducted until April 2020 . According to the Z value of left ventricular end diastolic diameter (LVEDD) measured by initial hospitalization echocardiography, the patients were divided into left ventricular enlargement group (LVEDD-Z> 2 ) and control group (LVEDD-Z≤ 2 ), and the clinical characteristics and prognosis between the two groups were compared. Results Sixty-one children were enrolled, including 14 patients (10 boys and 4 girls) in the left ventricular enlargement group with a median age of 5 months (ranging from 2 to 110 months) at diagnosis. In the control group, 47 patients (30 boys and 17 girls) had a median age of 6 months (ranging from 9 days to 14 years) at diagnosis. The proportions of heart failure, heart function class Ⅲ and Ⅳ and atrial premature beat were higher in the left ventricular enlargement group than those in the control group, and the differences were statistically significant (P< 55 % and diastolic function decline in the left ventricular enlargement group were higher than those in the control group, and the differences were statistically significant (P< 0 . 05 ). Five children in left ventricular enlargement group underwent genetic testing, and 3 children were tested positive to have MYH 7 with TTN gene mutation, MYH 7 gene mutation and glycogen storage disease type II respectively. Twelve patients in the left ventricular enlargement group were followed up and median follow-up time was 13 . 5 months. Five patients died, 4 of them died within 1 year after diagnosis, and all died of worsening heart failure. Conclusions The proportion of HCM in children with left ventricular enlargement is not low, which may be caused by mixed cardiomyopathy or heart failure, or may be related to metabolic cardiomyopathy, polygenic variation or gene expression heterogeneity.