Due to its advantages of direct heating, high temperature homogeneity, reaction rate enhancement, as well as energy savings, microwave-assisted polymerization has become a fast-growing field of polymer research. This paper reviews microwave-assisted polymerization, with an emphasis on the microwave-assisted ring-opening polymerization, covering both homopolymerization and copolymerization of the cyclic monomers. The advantages of microwave-assisted ring-opening polymerization over conventional polymerization are discussed briefly.