Abstract: In this paper, by taking Simple conceptual Climate Models (SCMs) and Earth system Models of Intermediate Complexity (EMICs) as research objects, simple climate models and their application in climate modeling are introduced. Simple conceptual climate models have become effective tools to understand the theory of climate and climate-change law. Earth system Models of Intermediate Complexity (EMICs) cover most of the components in the Earth system, and describe the process and feedback among the various components in more details. Because EMICs have low computational requirements, modeling applications of EMICs cover almost all fi elds of simple conceptual climate models and CGCMs simulations. EMICs will surely achieve a greater development and play a more important role in the Earth's climate simulation.