As large-scale infrastructure expansion has accelerated across China’s leading cities, the construction sector has grown quickly and the engineering materials industry has shifted from a relatively weak base toward stronger capabilities. This study develops a structured theoretical framework to clarify how engineering materials innovation operates within the construction industry, and then links this mechanism to regional growth using insights from economic growth theory. Employing a threshold regression model, the paper examines the relationship between engineering materials innovation and GDP growth in major Chinese cities. The analysis finds that the sector currently faces two key challenges: a slowing industrial growth rate and declining fixed-asset investment. Meanwhile, innovation outputs are becoming more diversified—reflected in rising diversity and ubiquity indices—though their rate of increase is moderating. Threshold regression estimates suggest that each 1% increase in engineering materials innovation is associated with a 0.099%–0.112% rise in regional GDP. Overall, the study offers a broader explanation of innovation-led economic development through the lens of engineering materials, enriches the literature on regional growth, and provides practical implications for public policy and firm-level innovation strategy.