The increase in travel mode options has led to changes in the travel decision-making behaviors of passengers and differences in spatial patterns of the markets of high-speed rail and air travel. Taking China’s central cities as the research subject, we analyze the spatial differentiation characteristics of high-speed rail and air transportation markets from a geographic perspective based on the passenger travel utility function. We analyze the influence on passenger travel decision-making behavior from the perspectives of the socioeconomic level and fare structure. The findings show that in the central city transportation market, passengers have a stronger preference for air travel. However, there are differences between regions, with high-speed rail dominating more in the partial north and air focusing on the partial south. As the value of time per capita increases, the dominant range of air travel gradually increases, while the dominant range of high-speed rail travel is compressed to some extent. An increase in fares does not cause a significant decrease in air demand; however, a reduction in fares leads to an increase in air passenger travel satisfaction.