Objective: To discuss the influence of electroacupuncture at "Neiguan" on myocardial morphology in rats with cardiac hypertrophy.Methods: Rats in the normal group received 3 mg/(kg·d) physiologic saline injection into the back skin, and rats in the model group received 3 mg/(kg·d) isoprenaline hydrochloride for 14 d; the electroacupuncture group received 3 mg/(kg·d) isoprenaline hydrochloride, and the acupuncture needles were penetrated 5 mm into the bilateral "Neiguan" acupoints and interconnected with a HANS electroacupuncture apparatus, in which the following stimulus parameters were selected: continuous wave at 2 Hz and 1 mA, for 20 min every day; rats in the P38 MAPK inhibitor group were injected 3 mg/(kg·d) isoprenaline hydrochloride and 0.3 mg/(kg·d) SB203580; rats in the electroacupuncture and P38 MAPK inhibitor group were injected 3 mg/(kg·d) isoprenaline hydrochloride and 0.3 mg/(kg·d) SB203580, and treated with electroacupuncture for 14 d.On the 15 th day, the body weights of the rats, as well as the weights of their left ventricle and of the whole heart were recorded; then left ventricular weight index and the heart weight index were calculated; hematoxylin-eosin staining was performed for the heart tissue.Results: Compared with the normal group, HW, LVW, HWI, and LVWI were significantly higher with statistical significance in model group(P<0.01); com pared with the model group, HW, LVW, HWI, and LVWI were significantly lower with statistical significance in the electroacupuncture group, the P38 MAPK inhibitor group, the electroacupuncture and P38 MAPK inhibitor group(P<0.05), but no significant difference between them(P>0.05).Compared with the model group, cardiomyocyte hypertrophy was improved, myocardial fiber arrangement became neat, and edema and hyperplasia were improved significantly.Conclusion: Electroacupuncture at "Neiguan" can decrease HWI, LVWI, and the average measurement of left ventricular wall thickness, and improve myocardial morphology significantly.