The protocol architecture of wireless personal area network is introduced,and based on this,the development of background,the status quo of relevant standards and role of RPL routing protocol are discussed.the RPL routing protocol related terms,working principle and the topological structure are in detail introduced.Finally,by example,how to generate the upward routes and downward routes by using three control messages by RPL routing protocol is introduced and the similarities and differences of down route creation mode of both Storing Mode and Non-Storing Mode are analyzed.