Following the paradigm of New Economic Geography, this study examines the impact of high-speed train (HST) services on the spatial structure of regional tourism economies in China. We collect panel data of 286 Chinese cities from 2007 to 2016 and adopt tourism-revenue location quotients to measure the relative agglomeration level of tourism economies for a city. According to the estimation results, tourism economies tend to agglomerate from the cities outside the HST network to those inside the network. Also, tourism economies start to disperse among cities within the network as more HST services become available. Furthermore, the results unveil the spatial heterogeneity of HST impacts. The moderating effects exerted by other transport modes are examined as well. Lastly, implications are provided for policy-makers and stakeholders on how to internalize the benefits from HST networks on tourism development.