The invention discloses a network function sharing method based on an extended vSDN (Virtual Software Defined Network). The method specifically comprises the following steps: receiving a request of auser of creating a network function, and selecting physical network functional equipment that satisfies user demand resources to create a network function instance for the user; using the ability of the SDN to control the network to guide network traffic of the user to the network function instance; and recording a mapping relationship between the network function instance of the user and the physical network functional equipment, and processing messages between the user and the user function instance accordingly. The invention further provides a system for implementing the above method. On the basis of the existing SDN virtualization framework, the network function sharing method and the system based on the extended vSDN provided by the invention realize the sharing of network functionalresources by multiple users through the automatic deployment of network functions.