Blockchain is one of the most influential technologies in the new round of digital economy development. In order to promote the prosperity of the digital economy with blockchain technology, we need to understand the essence of blockchain and the actual demands of relevant business. This paper delves into the nature of blockchain as a broadcast transmission technology from the perspective of technology evolution and analyzes the necessity of building a blockchain-based public Information Technology (IT) system. In addition, this paper analyzes the architecture, characteristics, and applications regarding trusted public IT system construction by drawing on the design ideas and architecture of Blockchain-based Service Network (BSN).