The construction of a high-speed railway is important to the transportation network and economic development of a region. To further understand the interaction between accessibility and urban economic linkage in the context of high-speed railway networks, this study investigated the spatial and temporal changes in the coupling coordination between accessibility and economic linkage after a high-speed railway was opened in Hunan Province, China, using a coupling coordination model. The aim of this research is to explore the role that high-speed rail construction plays in regional development. Results indicate that (1) after the high-speed railway was opened, the accessibility of cities in Hunan Province has improved significantly, although the overall pattern has not changed by much. This is because it still shows a radiation pattern, with the Changsha–Zhuzhou–Xiangtan urban agglomeration at its core, which has subsequently spread to surrounding areas; (2) the improvement in urban accessibility has strengthened the economic linkages between cities, and the overall spatial pattern has gradually evolved from a point-axis pattern to a network pattern. The bipolar trend of total regional economic linkage has become more pronounced than what it was before; (3) the overall coordination degree of accessibility and economic linkage coupling in Hunan Province is primary coupling, and the phenomenon of regional polarization is prominent, thus showing the overall spatial pattern of ‘strong in the east and weak in the west.’ Further strengthening the construction of the high-speed railway in the northern part of Hunan, promoting the economic construction in the western and southern parts of Hunan, and building a spatial pattern of synergistic integration for Hunan’s continued transportation and economic development are suggested.