As a basic activity of family business, intergenerational transition attracts universal attention of enterprise external stakeholders. Their evaluation of the legitimacy to successors will affect succession performance. However, the present research of organizational legitimacy judgment is still in the initial stage. Therefore, this study selects 23 listed companies as study cases and relevant investors’ comments to successors in 17 000 words. Considering the popularity of succession will gradually decrease with time, and a large number of irrelevant comments flood the available data, which will affect the accuracy of research, this study sets the relevant sample comments posted within 30 days after the handover. By using the data coding method of the Grounded Theory, this paper conceptualizes and categorizes shareholders’ comments respectively, and confirms 19 indicators of the legitimacy in family business successors. The research finally dissolves the legitimacy of successors into three dimensions: individual legitimacy, corporate legitimacy and family legitimacy. Individual legitimacy includes two main categories: biography and cognitive characteristics, such as gender, age, second generation identity, knowledge foundation, practical experience, leadership, and personality traits. Corporate legitimacy consists of two main categories of factors: inheritance management and organizational impression, such as withdrawal method, auxiliary measure, shift mode, insider behavior, power restructuring, the reason for abdication, political capital, and corporate reputation. Family legitimacy includes two main categories: family structure and family culture, such as family business identity, kinship, family cohesion, and family reputation. Then, this paper calculates the weights of the relationships between different indicators according to the different attention of criteria and applying Analytic Hierarchy Process （AHP）. Finally it builds a shareholder perspective of the legitimacy system of family business successors. The study finds that: in the first-level indicators, investors pay more attention to the related factors of corporate legitimacy, and the following is individual legitimacy and family legitimacy; in the three-level indicators, successor legitimacy factors from strong to weak respectively are the way of succession, kinship, insider behavior, company’s reputation, the age of successors, the leadership of successors, abdicated reason, and family reputation. This study not only deepens the understanding of the legitimacy of family business successors from a new perspective, but also provides a new idea for the cultivation of family business successors.