Steel structures are widely used worldwide for their high strength, light weight, excellent toughness, ductility and convenient construction, yet their inherent susceptibility to corrosion poses numerous challenges. This paper summarizes the research advances in steel structure anticorrosion, reviewing the corrosion mechanisms and influencing factors of steel structures in humid and hot atmospheric environments, and discussing the degradation effect of corrosion on their mechanical properties. It analyzes two main corrosion types, chemical and electrochemical corrosion, and how temperature, humidity, atmospheric pollutants and other factors accelerate the corrosion process. The paper also introduces the research progress in testing methods for steel structure corrosion, including the advantages and disadvantages of outdoor exposure tests, indoor simulation tests and electrochemical methods. In addition, it explores steel structure corrosion time-varying models that predict the temporal evolution of corrosion depth and rate in corrosive environments, and discusses the negative impacts of corrosion on mechanical properties—particularly how pitting corrosion and stress corrosion, two forms of local corrosion, cause reduced bearing capacity, local stress concentration and crack formation.