In recent decades, except for conceptual and three-dimensional comprehensive models (CGCMs), Earth system models of intermediate complexity (EMICs) as a new type of models occur in the scope of the Earth system models. EMICs simulate the interactions among several or even all components of the Earth system explicitly, albeit in a more reduced, i.e., more parameterized form. Thus EMICs describe the Earth system in an almost complete manner. Just due to their Simplicities, EMICs need more low Computation cost. Therefore, EMICs can not carry out only long-term simulations over 10 000 years, but a broad range of sensitivity experiments. EMICs have already become an integrated and powerful assessment tool for environmental studies, and bridge the gap between present CGCMs and conceptual models. In this review paper, status and improvements of EMICs are reviewed firstly. Then based on the domestic and foreign published literatures, the basic composition and application domain of EMICs in recent years are discussed. Finally, the future development trend of EMICs is forecasted.