［Objective/Significance］By sorting out phase separation theories，design strategies and existing bottlenecks of self-stratifying coatings，this paper lays a theoretical and practicalfoundation for technical breakthroughs. Future research is expected to advance their multi-functionalintegration and intelligent applications， expanding scenarios in emerging fields.［Analysis/Discussion/Progress］ The phase separation theories of self-stratifying coatings were systematically described，including density gradient-driven theory，Flory-Huggins theory，Hansen solubility theory and surface energy theory. Furthermore，the system design strategies were discussed in-depth，covering resin selection and combination，solvent system formulation，pigment and filler selection，additive incorporation，process parameter regulation and multi-functional synergy. The current technological bottlenecks in large-scale production，coating stability and precise control of structure and performance were clearly pointed out.［Conclusion/Prospect］Self-stratifying coatings， designed via phase separation theory，embody multi-layer advantages but face with bottlenecks like intricate production and poor film stability. Efforts should be done furtherly to advance theory，optimize preparation，expand its applications in areas such as multifunctional integration and intelligence，and facilitate industrialization.