The characteristics of city form contain the typological significance of thermal adaptability because of the region’s climate conditions and natural resources. From the perspective of thermal adaptability and environment mediation, the paper takes the humid temperate climate as the research scope. It takes the Alba as the study case to analyze the formation and evolution mechanism of urban forms under these climatic conditions. The paper first proposes a ternary external energy system model, urban regulation system, and human body reaction system. Then from the base of analyzing their interaction from the principle of thermal mechanism, the paper proposes the environmental physical factors that affect thermal comfort.