Recently, Radio over Fiber (RoF) technology has become a hot research topic in the broadband communication access network field and has attracted much attention in the industry. This is mainly because the technology makes full use of the massive bandwidth of optical fiber transmission and the application advantages of flexible coverage of wireless communication. In the evolution and development of RoF technology, multi-dimensional multi-order modulation has important scientific research significance and practical value because it can improve the system bandwidth utilization and reduce the signal transmission and receiving cost. This paper summarizes the research progress of traditional amplitude modulation, typical multi-dimensional multi-order modulation and some representative new multi-dimensional multi-order modulation technologies. We also briefly analyzes the application prospect of multi-dimensional multi-order modulation technology in RoF system.