This study aims to diagnose the limitations of the current advertising industry classification system, which fails to reflect the rapid restructuring of the advertising industry due to changes in the digital media environment, and proposes a new practical-oriented industry classification system. A qualitative research method was employed, conducting in-depth interviews with 15 experts from advertising industry practice and statistical research fields. The findings indicate that the current classification system inadequately captures the diversity of digital advertising, lacks clarity in distinguishing between industry categories, and fails to incorporate technology-based advertising sectors and platform-based advertising businesses adequately. Consequently, this study recommends several improvements, including detailed subdivision of digital advertising, introduction of an 'Advertising Platform Industry' category, and setting clear classifications for Ad-tech and Mar-tech companies. Additionally, the study emphasizes the necessity for the content industry’s specialized advertising classification to accurately reflect various types of digital advertising content. Ultimately, the research advocates unifying the advertising industry classification system and the content industry's special classification, thus accurately reflecting the real scale and structure of the industry, enhancing policy design, and facilitating international comparability and development in the advertising sector.