<p>The 4.0 technologies provide a technological window for regions to promote their innovation level and achieve leapfrogging. Using the panel data of China’s cities in the period from 2004 to 2021, this study finds the significantly positive impacts of technological window in technological innovation and technological catch-up and that these impacts are amplified by knowledge spillovers. Dividing regions into complex regions and simple regions based on their knowledge complexity, the roles of technological window and knowledge spillovers show heterogeneity. Complex regions are more sensitive to utilize technological window and knowledge spillovers to accelerate innovation and catch-up, while the technological window is less efficient for simple regions and these regions are difficult to absorb frontier knowledge spillovers.</p>