To observe the effects of ultrasound-guided stellate ganglion block (SGB) on cerebral oxygen metabolism and postoperative cognitive dysfunction (POCD) of elderly patients, we collected 80 elderly patients undergoing selective coronary artery bypass graft under cardiopulmonary bypass. The Mini Mental State Examination (MMSE) was applied to test the cognitive function. The SjvO2, Da-jvO2 and CEO2 were used for the analysis of the cerebral oxygen metabolism. We found that POCD was related to disequilibrium of cerebral oxygen metabolism. Ultrasound-guided SGB before surgery reduced the incidence of POCD because of the improvement of cerebral oxygen metabolism.