Objective: To observe the effect of needling Hegu (LI 4) on functions of the prefrontal cortex using the functional near infrared spectroscopy (fNIRS). Methods: A total of 12 healthy volunteers were randomly assigned to an acupuncture group (n=6) and a control group (n=6). The control group received no intervention. The acupuncture group received needling Hegu (LI 4) on the right side. The real-time concentration changes of oxygenated hemoglobin (HbO2), deoxygenated hemoglobin (d-Hb) and total hemoglobin (t-Hb) in the prefrontal cortex were recorded using the fNIRS, allowing for effect analysis of needling Hegu (LI 4) on the functions of the prefrontal cortex. Results: Compared with the control group, the HbO2 and t-Hb concentrations were increased in the acupuncture group and there were between-group statistical significances (bothP<0.05). There was no between-group statistical significance in d-Hb concentration (P>0.05). Conclusion: Needling Hegu (LI 4) can extensively activate the prefrontal cortex and therefore has significant effect on the functions of the brain's prefrontal cortex.