Despite China's massive infrastructure expansions in airports and high-speed railway (HSR), accessibility to these infrastructures from the passenger's perspective has yet been clearly analyzed and compared. The main objectives of this study are: (1) to evaluate accessibility by travel time between a given population grid cell and the nearest airport/HSR station, by accounting for both motorized vehicles and public transport; and (2) to measure and visualize the size of catchment area of an airport or a HSR station. We automatize the computation of free-flow road travel times, as well as the public transit times (by bus, subway, light-rail, tram and railway), from grid cells to infrastructure elements, by using a scalable routing framework. The Chinese air transportation network and HSR network are used as case studies to elaborate and evaluate the efficiency of our proposed framework. We find that the HSR network for China is much better accessible for the population than airports. Furthermore, grid cells with a high population density are much better connected to the Chinese transportation networks than other grid cells. Our methodology is generic in that it can be applied on an even larger scale (whole planet) and with different points of interest. Our work can help provide decision support for airport competition, privatization, and regulation, and for policy makers in infrastructure investment, in particular potential market and the location of new infrastructure elements.