In the evolution of traditional telecom network towards a converged next generation network, inter-working is always challenging due to different name spaces and routing mechanism across communities. Most existing Inter-working solutions are made at the terminal side. It requires mobile phone or PC users to install multiple client-side applications, such as, Google talk client, Skype client, and MSN client, etc. In order to avoid too many client applications running on mobile terminals, a network solution is desired. An IMS based Inter-working solution for multi-media services is proposed. It enables an IMS subscriber make use of a single SIP user agent to communicate with the other users who might have communication means other than IMS based devices. The solution consists of two parts: one is the conference like service; the other is the Inter-working gateway service.The detailed technical description of the proposed solution is described hereafter. The corresponding use cases are present. The solution can also be applied to “Group Communication”, e.g. ad-hoc group or pre-defined group multimedia service (Chat, Instant Messaging, Voice/video conference, etc.). The benefits of the proposed solution for end users and operators are discussed.