Modern service industry (MSI) is an information and knowledge intensive service industry, relying on information technology and modern management philosophy. The development of MSI is of high significance for promotin g rapid global economy, accelerating social progress, and realizing the general strategy of building an innovation-oriented society and harmonious realm. This paper gives an overview of the worldwide MSI development status, especially introduces the development of MSI in China. Our survey of 62 MSI-related listed firms in China shows that Crossover Service emerges everywhere including their business models, product, and services. Thus, we propose the concept of Crossover Service and introduce its 3C-features (Crossover, Convergence, and Complex), the scientific issues, the technique framework and the challenges. And also, we give a brief introduction of our middleware platform named JTang++, which supports the lifecycle of Crossover Service well.