From the perspective of model coupling, this paper introduces the research progress of the current damage function of integrated assessment model(IAM). It mainly analyzes the coupling function and existing scientific problems of the damage function from the point of view of the construction method of the damage function, the coupling of the damage function with the climate model and the economic model, and the coupling IAM with climate model, then discusses its improvement direction. On the construction method of the damage function, it mainly adopts the expert judgement, meta-analysis and statistical methods. However, each of them has both advantages and disadvantages. While coupling with the climate model, most of damage functions only contain the temperature rise as the climate change factor, which can't express the precipitation and other climate change information. And it is calibrated by the annual average temperature at the global scale, which can't reflect the regional differences and the seasonal changes and can't directly describe the huge damage caused by extreme climate events. On the coupling with the economic model, the damage function based on the production sectors are lacking in the assessment function of indirect damages and the dynamic influence mechanism of economic growth. In view of above shortcomings of feedback mechanism of the economic impacts of climate change in IAM, the damage function mainly needs to be reconstructed from two directions, namely, the refinement of regional climate change factors and the subdivision of the economic sectors. Thus, it can closely link the climate module with economic module and comprehensively assess the economic damages from climate change. In addition, it is necessary to solve the problem of spatial and temporal scale mismatching in the coupling economic model and climate model to finally provide an important solution for the coupling of IAM model with the climate model and even the earth system model.