Guanzhong Plain urban agglometration are significant hubs for tourism resources in western China, and the development of its many tourism resources and balanced socioeconomic development require the support of high-speed transport and other infrastructure. In the context of the strategy of a strong transportation country and the development of “transportation and tourism integration”, theoretical research and empirical analysis on promoting the coordinated development of high-speed transportation and the tourism economy can provide support for transforming and upgrading transportation and tourism industries in urban agglomerations. This study focuses on the Guanzhong Plain urban agglometration, utilizing a comprehensive evaluation index system of high-speed transportation and tourism economy. It employs methods such as the entropy value method, the coupling coordination model, and the kernel density function to analyze the comprehensive development of high-speed transportation and the tourism economy. It also analyzes the evolution trend of their coupling coordination over time and space dimensions and examines the differences in the coordinated development of various high-speed transportation modes and the tourism economy. The results show that: (1) The overall comprehensive level of high-speed transportation and tourism economy of Guanzhong Plain urban agglometration is increasing, but a significant developmental difference exists within the city cluster, presenting the phenomenon of uneven development of “one big, and other small”. (2) The high-speed transportation and tourism economy of the city cluster have not yet formed a clear pattern of coordinated development, with their coupling and coordination degree gradually rising over time and evolving to the pattern of “one circle, one axis, and three belts” in space. (3) Large differences exist in the coordination degree of the system and the marginal effect of the tourism economy among different high-speed transportation combinations, and the coupled coordination values of different high-speed transportation modes and the tourism economy differ. Hence, it is necessary to strengthen the overall collaborative effect of the city cluster transportation network, leverage the core driving role of Xi’an City, and accelerate the construction of the Guanzhong Plain urban agglometration high-speed transportation and the coordinated development pattern of the tourism economy.