Objective · To assess left ventricular torsion function and systolic synchronization in children with hypertrophic cardiomyopathy (HCM) by using two-dimensional speckle tracking echocardiography (2D-STI), so as to provide theoretical basis for early clinical evaluation of cardiac function in children. Methods · Twenty-nine children with HCM in Shanghai Children’s Hospital, Shanghai Jiao Tong University from October 2018 to March 2019 were divided into two groups according to whether having clinical symptoms, i.e., asymptomatic HCM group (n=17) and symptomatic HCM group (n=12). Thirty normal children were also enrolled in the normal control group. All subjects underwent echocardiography, and the torsion-and strain-related data of the whole and different myocardial segments in the cardiac sections of left ventricle were obtained by 2D-STI. Results · Left ventricular strain analysis showed that the left ventricular longitudinal strains of both HCM groups decreased significantly compared with the normal control group (P<0.05), while the radial and circumferential strains increased significantly (P<0.05). The maximum difference of peak time in different segments on six cardiac sections in the symptomatic HCM group was significantly higher than that in the normal control group (P=0.000), while the difference between the asymptomatic HCM group and the normal control group was not significant. Left ventricular torsion function analysis showed that the global peak twists of left ventricle and positive peaks of rotation velocity in both HCM groups were significantly higher compared with the normal control group (P<0.05), standardized times to peak were longer (P<0.05), and negative peaks of rotation velocity and the untwisting rates were lower (P<0.05). Conclusion · In the children with HCM, the left ventricular torsion function is enhanced and diastolic function is weakened. In the symptomatic children, the left ventricular systolic synchrony is poor.