In the context of integrating culture and tourism, world heritage tourism research has become a focus in tourism research in recent years. There are increasing discussions in academic circles on the content and methods of this field. Clarifying the knowledge system of research is conducive to dialogue with international theoretical frontiers and integrating, analyzing, and predicting the progress and lineage from a more comprehensive perspective. Still, few studies on the knowledge system of world heritage tourism research have been conducted. To fill this gap, this study uses the SSCI and SCI sub-databases of Web of Science Core Collection as the data source with the help of CiteSpace and VOSviewer software to measure the knowledge system of world heritage tourism research. A bibliometric analysis of 567 publications between 1992 and 2020 was conducted to construct a framework of a knowledge system based on literature statistics and content analysis, revealing the geographic research regions, theories and methods, themes and contents, trend evolution, and future research inspiration. The results show that: (1) the number of publications tends to increase gradually, with the highest in 2019. The authors and research institutions are mainly concentrated in Europe, America, East Asia. China has the highest publications. More literature on cultural heritage as a geographical study area than natural heritage. (2) The research themes, objects, and methods of the sample literature have become more diversified with the advancement of the research stage. The literature on multi-stakeholder research is the largest, followed by tourism impacts and research on World Heritage Sites’ resource management techniques and methods. These studies provide a multifaceted interpretation of the sustainable development of World heritage tourism, mainly from the perspectives of both supply and demand. However, the theoretical system is still incomplete. (3) Future research should strengthen the theoretical system construction, research innovation, cooperation, and research exchange in world heritage tourism research. Pay more attention to the research on the pluralistic value system of world heritage. Focus on exploring research on world heritage tourism’s resilience and localization dilemmas under the impact of the New Crown epidemic. To reveal the synergistic mechanisms and paths of diversified livelihoods of World Heritage Sites’ residents in ecologically fragile and impoverished areas.