Smart cities are the product of the integration of China's new urbanization and informatization. Inclusive green growth (IGG) is an important strategic idea for economic development and transformation. This study uses CRITIC-entropy weight method to quantitatively measure IGG index from the three dimensions of economic growth, green growth and inclusive growth. Based on the panel data of prefectural cities in China from 2006 to 2022, this study evaluates the impact of smart city construction on IGG using multi-period difference-in-differences and spatial difference-in-differences models. The results show that smart city construction has a significant positive impact on IGG, as well as economic growth, green growth, and inclusive growth. Meanwhile, the impact of smart city construction on IGG has significant regional heterogeneity. Mechanism test shows that smart city construction positively affects IGG through three dimensions of technology, talent, and governance. Furthermore, there is a spatial spillover effect in smart city construction, which significantly promotes economic growth and green growth in neighboring non-pilot areas, as well as economic growth in neighboring pilot areas. This study provides valuable theoretical insights and policy ideas for planning in emerging economies to promote high-quality development and ecological civilization through smart city strategy.