How to improve the spectrum utilization efficiency to support difference services in specific frequency band is becoming more and more critical issue considering the limited spectrum resource, and the spectrum sharing is the only way out. The traditional approach on spectrum usage among different industries especially between satellite and terrestrial industry need to be changed from competition toward convergence. With the fast development of satellite communication network, it will play an important role in B5G and 6G communication network evolution. In this paper, the expanded new scenarios and applications with the integrated satellite and terrestrial networks, as well as new enabled technologies in different stage of integrated networks are analyzed, while relevant study and standardization work are investigated in both ITU-R and 3GPP. Finally, the observations on key challenges on interface and network technologies, as well as regulation issues on spectrum sharing for the integrated networks are provided.