<p>SnS, a well-known van der Waals chalcogenide, is susceptible to oxidation in high-temperature or high-humidity environments, significantly impacting its functional performance and device stability. Conversely, oxidation can be used as an effective strategy for surface engineering, allowing for structure modulation or design, property tuning and application exploration. However, there is currently a gap in understanding the relationship between the oxidation behavior of SnS, the structure of its oxidized surface, and the dependence on oxidation temperature. In this study, we systematically investigated the evolution of SnS surfaces under thermal oxidation using electron microscopy. The microstructure evolution (e.g., surface structures, phases, defects, and interface) of SnS during high-temperature oxidation has been fully characterized and studied based on cross-sectional samples. Various surface heterostructures were constructed, including SnO₂/SnS, SnO₂/SnS₂/SnS, and SnO₂/Sn₂S₃/SnS, offering significant potential for the surface functionalization of SnS-based systems. Accordingly, oxidation mechanisms at different stages were elucidated based on the detailed and clear picture of microstructures. This research not only deepens our understanding of the fundamental science of SnS oxidation but also provides valuable insights for preventing and developing surface oxidation engineering in SnS and other van der Waals chalcogenides/materials.</p> Graphical abstract <p></p>