MSTP (Multiple Service Transport Platform) makes up the shortcoming of data processing of SDH (Synchronous Digital Hierarchy), and implements Ethernet,ATM(Asynchronous Transfer Mode),and RPR(Resilient Packet Ring) which implement the mapping and transmitting signals to virtual container. It is of great significance for network upgrading or MAN construction.Based on discussion of SDH, several critical technologies for MSTP are under investigation. Frame format and frame location method are discussed in GFP (Generic Framing Procedure) encapsulation technology, and framed mapping and transparent mapping are also discussed. In concatenation technology, the definition and differences of consecutive concatenation and virtual concatenation are presented and the constitution graphic for virtual concatenation member group is depicted. The two ring adverse topology and meaning of RPR is discussed. The physical layer and A, B, C types of service types supported by it is analyzed. The queuing technology of RPR, Global fairness algorithm, two types of service protection is detailed discussed, topology discovery and management functions of RPR are discussed.The basic principals and methods of MSTP are provided. MSTP consists of SDH part and data part. In SDH part, SDH framework graphic and function modules that implement traditional functions are discussed.The success of MSTP integrates the data network with voice network and facilitates the lay out of network of Internet Service Provider and thus make full of network resource.