The paper defines the intension and extension of brand by using research methods of philosophy, literature survey, summarization, history, induction, deduction, comparison and systematic research. The maim conclusions of qualitative research show that public awareness of the intension of brand experienced a dialectical process of waxing and waning of materialization, personification and characters complexification of brand. Different professional fields have different emphases on the characteristics of brand, and it gradually reflects some different substantive characteristics. People can create a brand for everything that needs communication and can be communicated. The extension of brand is relatively broader while the intension is narrower. Most existing brand definitions have problems of inaccuracy, insufficiency, redundancy, using circular definition or using a part as the whole and so on. Based on this, the paper puts forward a new literal definition of brand. Finally the paper discusses the trend of multi-subject comprehensive development of brand research.