Abstract: Multimodality imaging is the general trend of clinical imaging.PET-CT is one of the most classic and mature multimodality imaging methods and is widely used today.MRI is another kind of conventional imaging method, in contrast to CT, MRI can not only yield images with higher soft-tissue contrast and better spatial resolution but also provide some functional information by special imaging techniques such as MRS.The combination of PET and MRI for simultaneous data acquisition should have far-reaching consequences for clinical and scientific study.This review describes the progress to date and talks about the problems met in the development of PET-MRI and look forward to its potential application.