<p>A thorough understanding of theoretical connotations, level evolution, and interactive mechanism of population development and modernization construction is a pivotal element in advancing regional sustainable development. Leveraging statistical data collected from Sichuan over the period spanning 2013 to 2022, this research employs the entropy method and the critic-topsis method to measure the level of population development and modernization construction in Sichuan. Subsequently, utilizing the coupling coordination degree model to conduct a scientific assessment of the synergistic impact between population development and modernization construction in Sichuan. The empirical results show that the level of population development shifted from 0.255 to 0.724 while the level of modernization construction shifted from 0.236 to 0.810, which reveals the population development and modernization construction in Sichuan have exhibited an overall upward trend during the sample period. The stability of population quantity, the enhancement of population quality, the optimization of population structure, the rationality of population distribution, and the improvement of the correlation effect between population and external systems has collectively propelled the level of population development. And the enhancement of economic development, the accumulation of technological innovation, the optimization of public service, the improvement of ecological environment, and the enhancement of openness have jointly contributed to the elevation of modernization construction. Additionally, the interaction intensity between population development and modernization construction in Sichuan keeps above 0.9, and the interaction effect has successfully transitioned from an unbalanced state to a coordinated one. Supporting Sichuan’s modernization construction with population development and leading population development with Sichuan’s modernization construction are apt description of the current development situation in Sichuan. Furthermore, the population development and modernization construction in Sichuan will continue to encounter cyclical obstacles and non-systemic hurdles, while the positive growth trend is irrevocable. Based on the above conclusion, this study provide the corresponding implication for reference.</p>