Chinese modernization is a crucial proposition for realizing the great rejuvenation of the Chinese nation in the new era, and high-quality development of social security is a major task for achieving Chinese modernization. This paper measures Chinese modernization and high-quality development of social security in 31 provinces (autonomous regions and municipalities) of China from 2013 to 2022 by constructing a multi-dimensional evaluation index system. It introduces the spatial Durbin model to analyze the impact of high-quality development of social security on Chinese modernization. This paper finds that the overall level of Chinese modernization and high-quality development of social security shows an upward trend. In terms of regional differentiation, the two exhibit a spatial distribution pattern of “leading in the eastern region, developing in the central region, and progressing in the western region”. In terms of dimensional differences, both exhibit structural imbalance and unbalanced growth. The high-quality development of social security, characterized by inclusiveness, sufficiency, fairness, development, sustainability, and security standardization, has promoted Chinese modernization in five dimensions of breadth, intensity, depth, height and warmth. The promoting effect of high-quality development of social security has not only long-term and overall characteristics, but also regional heterogeneity. The eastern region has a higher level of high-quality development of social security and Chinese modernization, but the effectiveness of high-quality development of social security in contributing to Chinese modernization is relatively weak. In addition, both the high-quality development of social security and Chinese modernization show positive spatial spillover effects. The improvement of the high-quality development of social security and the level of Chinese modernization in a region has a spillover effect on the spatially related areas, promoting Chinese modernization in those areas. It is suggested to focus on overall development, enhance the high-quality development of social security, reduce the structural gap in different dimensions, strengthen the positive spatial spillover effect, and promote balanced structural development and coordinated regional development, thereby achieving Chinese modernization.