Objective:To establish the haemodynamic response during the verbal fluency task(VFT)in patients with MCI and to find a screening tool that could be used as a predictor of dementia. Method:Functional near-infrared spectroscopy(fNIRS)can detect changes in blood oxygen in the brain,thus revealing the patient's functional brain activity status,and is used to study the level of brain function in MCI.We evaluated the hemodynamic response in the prefrontal and temporal regions of MCI patients and healthy controls in our study. Result:The results found a significantly reduced haemodynamic response in the prefrontal brain regions in the MCI group. Conclusion:The results suggested that a reduced haemodynamic response in the prefrontal brain regions could be used as a diagnostic biomarker for dementia.