[Abstract] Objective：To explorer the effect of valsartan on the expression of CaMKII in Juvenile rat with Heart Failure(HF). Methods: The animal model of heart failure was established by abdominal aortic constriction （AAC）in 3 weeks old SD rats ，while the establishment of the sham operation group. 4 weeks later

the rats with heart failure were randomly divided into 2 group：HF group，valsartan treatment group. Valsartan were taken through direct gastric gavage everyday. HF group and sham operation group were given placebos.8 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 the sham operation group (n=8)， 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)，the expression of CaMKII was increased by 1.95 fold (F =7.541，P =0.026)

the expression of CaMKII subunits (δB δ9) was increased to 1.93 fold (F =7.042，P =0.029)，and the expression of CaMKIIδC was increased to 1.93 fold (F =6.714，P =0.045) in HF group(n=10). After the treatment，no significant difference of LVIDs、LVIDd 、LVESV、LVEDV 、LVEF 、LVFS 、LVMI and the expression of CaMKII was found between valsartan treatment group and sham operation group（P >0.05）. Conclusion: The expression of CaMKII in juvenile rats with HF was increased. Valsartan can improve cardiac contractile function with heart failure

which may be associated with reduced expression of CaMKII in ventricular myocytes .