Interdiffusion behavior at the interface between high-temperature protective coatings and single-crystal superalloys is a critical issue affecting the service life and reliability of aircraft engine turbine blades. With the continuous increase in turbine inlet temperatures of aircraft engines, the elemental interdiffusion between coatings and single-crystal superalloys has become particularly serious. This article systematically reviews the interdiffusion process between high-temperature protective coating and single-crystal superalloys systems, clarifying the formation mechanisms of the Interdiffusion Zone (IDZ), Substrate Diffusion Zone (SDZ), and Secondary Reaction Zone (SRZ). The influencing factors and laws of the interdiffusion behavior and mechanical properties of coatings/single-crystal superalloys are explored from the perspectives of single-crystal composition, orientation, thermal-mechanical coupling environment, and thin-wall effect of single-crystal superalloys. Additionally, this work reviews recent research advances and identifies persistent challenges associated with interface control methodologies for diverse coating systems and single-crystal superalloys, and proposes targeted design strategies along with prospective directions for future development.