As demanders of medical services，patients often have a tendency to seek medical treatment in tertiary hospitals，resulting in a run on medical resources in tertiary hospitals. The emergence of a hierarchical diagnosis and treatment system is an important means to alleviate the pressure of outpatient and emergency treatment for doctors in tertiary hospitals，guide patients to seek medical treatment in an orderly manner，and solve the“difficulty of seeking medical treatment” for patients. Megacities have complete medical service systems，abundant medical resources，and high-level medical services. This article provides an overview of the construction of Internet hospitals in megacities and the application of Internet hospitals in hierarchical diagnosis and treatment systems. It analyses the existing problems and proposes countermeasures and suggestions from the perspective of megacities.