Abstract: The high-speed rail has become a key factor affecting the integration of regional tourism in China. However, the absence of systematic view considering tourism supply and demand separately is widespread in the existing researches on the impact of high-speed rails on tourism. In this paper the regional tourism competitiveness and resident travel potential with and without high-speed rail network of the Yangtze River delta are studied using GIS and the improved gravity model of tourism system. Meanwhile, the specific direction, degree and meaning of the regional tourism integration under the impact of high-speed rail are also analyzed. The results show that: (1) the high-speed rails’ impact on regional tourism integration has enhanced, which has widened the hierarchical difference and meanwhile caused the integration effect of reverse balance; (2) the high-speed rails have strengthened the core-periphery structure of regional tourism system, and tourism competitiveness and resident travel potential of none-HSR cities have been weakened while those of the core HSR city Shanghai has enhanced; (3) after the operation of the high-speed rails, the tourism pattern has changed most in periphery areas; however, the non-balanced development of regional tourism in these areas cannot be changed fundamentally because of comprehensive location disadvantages; (4) the time-space compression of high-speed rail weakens the effect of distance meanwhile strengthens the effect of tourism itself, so to develop tourism integration of high-speed railway cities should pay attention to the differential development strategy so as to avoid the homogenization of competition; and (5) the high-speed rail can provide a relatively equitable transportation development platform for the peripheral cities and prevent periphery areas from being further marginalized. Therefore, we put forward several specific policy proposals to establish a regional balanced HSR network and promote regional tourism integration development.