Unified Communication (UC) has been one of the hot topics in telecommunication field, and venders introduce various platforms and products for it. Due to the diversification of platform technologies and lacking of unified application interface, curtent applications are hard to be extended and interconnected. Taking example for China Netcom NGN open service platform, this paper briefly presents how to build up carrier-grade unified communication applications under the direction of operator, which will be the reference to make fast development and large scale deployment for UC services.