Objective: To investigate the effect of acupuncture on brain cortex of unconscious patients by observing the changes of EEG nonlinear properties. Method: Thirty unconscious patients were involved in this study. EEG was recorded in all subjects under three states: eyes closed, acupuncture stimulus on hemiplegic side and healthy side. EEG nonlinear indexes such as correlation dimension (D2), complexity (Cx) and approximate entropy (ApEn) were calculated for all subjects. Result: The effects of acupuncture stimulus on hemiplegic side and healthy side had no significant difference compared with eyes closed state (P>0.05), but the D2 nonlinear indexes of most patients were kept at a rising trend. Conclusion: Acupuncture might provide some awaking effect on the unconscious patients, but the effect of acupuncture on the severe brain trauma or stroke might be limited. EEG may display some immediate effect of acupuncture on brain cortex.