Objective：To explore the effects of valsartan on expressions of calmodulin-dependent protein kinaseⅡ（CaMKⅡ） in juve－nile rats with heart failure（HF）. Methods：HF animal model was established by abdominal aortic constriction（AAC） in 3 week-old SD rats while sham operation group was established. Four weeks later，rats with HF were randomly divided into 2 groups：HF group and valsartan treatment group. Rats in valsartan treatment group were given valsartan through direct gastric gavage everyday while those in HF group and sham operation group were given placebos. Eight weeks later，high frequency ultrasound was employed to measure left ventricular-internal dimension systole（LVIDs），left ventricular-internal diastolic diameter（LVIDd），left ventricular end-systolic volume（LVESV），left ventricular end diastolic volume（LVEDV），left ventricular ejection fraction（LVEF），left ventricular fractional shortening（LVFS） of rats. Left and right ventricular mass index（LVMI，RVMI） were calculated. Western blot was applied to detect the expression of CaMKⅡ and subunits. Results：Compared with those in sham operation group，LVIDs and LVESV were increased（F=21.082，P<0.001；F=14.178，P=0.001），LVEF and LVFS were all significantly decreased（F=103.766，P<0.001；F=62.953，P<0.001），LVMI was increased（F=13.272，P=0.01），expressions of CaMKⅡ were increased by 1.95 folds（F=7.541，P=0.026），expressions of CaMKⅡ subunits（δB+δ9） were increased by 1.93 folds（F=7.042，P=0.029） and expressions of CaMKⅡδC was increased by 1.93 folds（F=6.714，P=0.045） in HF group. After the treatment，no significant difference in LVIDs，LVIDd，LVESV，LVEDV，LVEF，LVFS，LVMI and expressions of CaMKⅡ was found between valsartan treatment group and sham operation group（P >0.05）. Conclusions：Expressions of CaMKⅡ in juvenile rats with HF are increased. Valsartan can improve cardiac contractile function of rats with HF，which may be associated with reduced expressions of CaMKⅡ in ventricular myocytes.