Abstract: Among the five major senses, olfaction is the most common, ancient, direct and intrinsic.The special characteristics of the olfaction system have made its study so difficult that up to now we are still unclear about the olfactory functions in human beings and the mechanisms in the brain. As in the cases of other technologies based on physical principles, magnetic resonance imaging (MRI) and related methods have greatly advanced our understanding of the entire field of life science. Functional MRI, a non-invasive and non-radioactive imaging method with high spatial resolution and contrast, provides us with a powerful tool to investigate the brain mechanisms for a variety of olfactory functions and behavior. In this review, we will first give a brief introduction to the olfactory system, then focus on the major findings in human olfaction revealed by the application of functional MRI in the past decade.