The aim of the study was to evaluate the left ventricular systolic function of newborns with asphyxia using tissue Doppler imaging (TDI). Newborns with a history of asphyxia were divided into severe and mild groups based on their Apgar scores; normal newborns without asphyxia served as the controls. Left ventricular ejection fraction (LVEF), fraction shortening (FS), and stroke volume (SV) were measured by M-mode echocardiography at 24, 48, and 72 h after birth. The peak systolic velocity of the anterior mitral valve leaflet (Sm wave) was measured with TDI. Cardiac troponin I (CTnI) was measured. The results revealed that the LVEF and FS of the severe asphyxia group at 24 h were significantly lower than those at later time points (P < 0.01). These parameters were also significantly lower than those of the mild and control groups (P < 0.01). SV was not significantly different among the three groups. Sm wave of asphyxia groups was significantly lower than that of control group (P < 0.001). In the severe asphyxia group, Sm wave at 24 h was significantly lower than that at 48 or 72 h (P < 0.001). CTnI values of the severe asphyxia group were remarkably higher than those of the other two groups (P < 0.01). The findings of this study indicate decreased left ventricular systolic function of newborn children after asphyxia. Sm by TDI is a more sensitive indicator of left ventricular systolic function than LVEF, FS, or SV by M-mode echocardiography.