<p>Thermal management at the nanoscale is critical for advanced semiconductor and quantum technologies. Topological diffusion enables robust and unidirectional heat transport, but its application to nanoscale systems, where quasi-ballistic phonon transport dominates, remains largely unexplored. Here, we demonstrate a design principle for topological thermal diffusion in one-dimensional silicon nanostructures based on the Su-Schrieffer-Heeger model. By incorporating size-dependent effective thermal conductivity into a diffusion-based topological framework, we account for nanoscale phonon transport within an effective model. The predicted decay rates agree well with experimentally measured decay rates of strongly localized topological interface states, validating the model as an effective description of nanoscale thermal transport through parameterized thermal conductivity. Our results establish a practical framework for engineering topological heat transport in nanoscale systems which include semiconductor-based quantum and thermoelectric devices, providing a unified and scalable framework for topological thermal management across diverse scales.</p>