Objective: To study the early diagnositic value of olfactory bulb volume measurement with MRI to Alzheimer’ disease. Methods: Total of 31 patients with Alzheimer’ disease(AD) and 31 healthy elderly control was measured about olfactory bulb volume and hippocampal volume with magnetic resonance imaging (MRI). Their congnition function were measured by mini-mental status examination(MMSE),relationship between MMSE and olfactory bulb volume or hippocampal volume were analyzed. Results: AD group was significantly atrophy compared with the controls in olfactory bulb volume and hippocampal volume(P < 0.01). The correlation in AD group was found between hippocampal volume and MMSE scores (r = 0.44,P < 0.05),and between olfactory bulb volume and MMSE scores (r = 0.49,P < 0.05). A significant correlation in AD group was found between olfactory bulb volume and hippocampal volume (r = 0.69,P < 0.01). The specificity and sensitivity of olfactory bulb volume measurement with MRI to Alzheimer’ disease are respectively 0.65 and 0.78. The specificity and sensitivity of hippocampal volume measurement with MRI to Alzheimer’disease are respectively 0.91 and 0.74. Conclusion: Olfactory bulb volume in patients with AD was significantly smaller,and has significant correlation with congnition function reduction,but the diagnostic accuracy of olfactory bulb volume measurement with MRI to AD is no better than that of hippocampal volume.