There exist varieties of feedback mechanisms in climate system, and the different description of these climate feedback mechanisms within climate models is one of the major causes for the different responses of these models to the same direct radiative forcing (e.g., doubling CO2). Only when these mechanisms are fully understood and then properly represented, these climate models can be applied to the projection of future climate changes. As the first part of this paper, some basic concepts (e.g., climate sensitivity parameter, cloud radiative forcing, etc.) which are widely used in the analysis of climate feedback mechanism will be introduced, and then several methods will be summarized along with their advantages and shortcomings. The detailed analysis of climate feedback and mechanisms will be given in the second part of this paper.