This chapter analyzes the spatio-temporal development of high-speed rail (HSR) accessibility in China from 2008 to 2023, employing weighted average travel time (WATT) and the coefficient of variation (CoV) to evaluate average accessibility levels and regional differences. The results indicate a significant national enhancement in accessibility, with average travel time reduced by more than 15 h, demonstrating a pronounced time-space compression impact. Nonetheless, improvements in accessibility were markedly inconsistent between regions, city scales, and metropolitan areas. Eastern and major cities experienced earlier and more significant advantages, whereas the western region, smaller cities, and peripheral areas fell behind, although some later exhibited remarkable catch-up growth. The findings suggest a trend of “initial divergence followed by partial convergence,” highlighting the dual function of HSR in both exacerbating and, under specific circumstances, alleviating regional disparities.