As an example of applying chemical heterogeneity for new microstructure design concept, this study investigates the role of chemical heterogeneity in the microstructure evolution of low carbon steel during quenching and partitioning (Q&P) treatment and its subsequent impact on mechanical properties. The research specifically examines the characteristics of chemical heterogeneity before the Q&P process, focusing on the extent of Mn enrichment and the scale of Mn-enriched domains. The results demonstrate that Mn chemical heterogeneity is pivotal in enhancing both strength and ductility post-Q&P treatment. However, the distinct characteristics of this heterogeneity influence strength and ductility through different underlying mechanisms, highlighting the need for precise control of these heterogeneities to maximize their potential in advanced microstructure design strategies.