As a measure adopted to reform China's higher education, Business English has been established as an undergraduate major by the Ministry of Education of PRC. Relative to the rapid domestic development of Business English professional education, the research on Business English as an academic discipline is lagging in general, bringing about a fairly weaker theoretical foundation and hindrances to the disciplinary development of Business English. In the academic circles, Business English discipline remains an issue less clarified and calls for more studies that present deep and comprehensive understanding. The author, in this paper, based on a literature review, discusses the nature of Business English, analyzes and summarizes from the perspective of ESP studies the unique features of Business English. By regarding Business English as the Lingua Franca in business communication, the author explains the symbiosis and multi-dimensionalities that Business English has in nature and identifies the disciplinary boundaries and contents of Business English. Moreover, the author explains critical issues related to intellectual discipline of Business English, such as the definition, the research objects, the features, the research fields, the theoretical systems, and the research methodology/methods, and thus identifies the framework and components that constitute the discipline of Business English.