OBJECTIVE To observe the effect of electroacupuncture (EA) stimulation of "Neiguan" (PC 6) and "Sanyinjiao" (SP 6) on morphological changes, myocardial energy metabolism in rats undergoing simulated weightlessness. METHODS A total of 40 male Wistar rats were randomly divided into normal control, weightlessness model, Neiguan (PC 6) and Sanyinjiao (SP 6) groups (10 rats/group). EA was applied to PC 6 and SP 6 acupoints for 30 min, once every other day. The morphological changes were observed by light microscopy after H. E. staining. Lactate dehydrogenase (LDH), succinate dehydrogenase (SDH) and ATPase activities in the left ventricular myocardium were measured by colorimetry. RESULTS In weightlessness rats, myocardial pathological changes as loose arrangement, breakage and lytic necrosis of myocardial fibers were found, these changes were obviously improved in rats of both PC 6 and SP 6 groups. Compared with the control group, the ATPase activity was significantly decreased, while the LDH activity was significantly increased in the model group (P<0.05). After EA intervention, the ATPase activity was obviously increased in the SP 6 group (P<0. 05), and LDH activity was apparently reduced in both PC 6 and SP 6 groups (P<0. 05). No significant changes were found in myocardial SDH activity after modeling and EA of the two acupoints (P>0. 05). CONCLUSIONS EA intervention has functions in up-regulating ATP activity and suppressing the myocardial LDH activity in weightlessness rats, which may be related to its effect in improving myocardial pathological changes.