Multi-RAT access network, or heterogeneous access network, is considered to be the key enabling technology to satisfy the 5G requirements, such as high data rate, ultra-low latency and reliability. To make efficient use of all the available network resources, various research activities on multi-connectivity have been proposed to simultaneously connect, steer, and orchestrate across multiple different radio access technologies. Standardization of the management and orchestration of multi-connectivity environment, however, has just been initiated, thus further research and development is required. This paper proposes a novel management and orchestration architecture for integrated access of satellite and terrestrial in 5G. It especially focuses on the traffic steering and load-balancing of heterogeneous multi-RAT access environment.