Energy Internet is the key of meeting the ever-increasing energy demand and building a sustainable energy eco-system in the future. As the fundamental physical realization of the Energy Internet, integrated energy systems (IES) need to be properly planned to ensure the safe, efficient and low-carbon operation in later stages. Firstly the basic planning methods for various individual energy systems and the general framework of IES planning are introduced, and the models of coupling elements among different subsystems are combed. Literatures in the field of joint planning of electricity-gas coupling systems and electricity-gas-heating/cooling coupling systems are classified according to the types of subsystems involved and are analyzed in detail. Finally, the limits of current work as well as potential research topics in this field are proposed.