Assessing the impact of future global warming is impeded by the large range of Equilibrium Climate Sensitivity (ECS) to atmospheric CO2 doubling. Previous studies suggested the Last Glacial Maximum ( LGM) is an ideal paleoclimate period to constrain the ECS since the abundant proxy data and coupled model simulations. However, the ECS inferred from LGM proxy data is still elusive since the climate feedback processes have not been well understood. In this study, the similarities and differences in the climate feedbacks, include temperature, water vapor, albedo and cloud feedback, for LGM and abrupt4xCO2 scenarios are investigated using the radiative kernel method and the Paleoclimate Modelling Intercomparison Project Phase Ⅲ (PMIP3) coupled model simulations. The results suggest that,in the global mean sense,the temperature,water vaper and albedo feedbacks have significant difference between LGM and abrupt4xCO2 scenarios, while the cloud feedback process is undistinguishable due to its uncertainties between scenarios and/or coupled models. The spatial distributions of feedback strengths are different in all feedback processes between scenarios. The discrepancy of temperature feedback between LGM and abrupt4xCO2 scenarios are due to highly inhomogeneous of surface temperature response due to the presence of continental ice sheets and tropical convection change because of the exposure of continental shelf. The difference in water vapor feedbacks over the equatorial eastern Pacific could be induced by the exposure of continental shelf and its induced Walker circulation change. The change of albedo feedback is consistent with the change of continental ice sheets/sea ice cover. The model uncertainty in cloud feedback strength and the change of low cloud between LGM and abrupt4xCO2 scenario could affect the total cloud feedback strength. Individual LGM forcing sensitive experiments are necessary for isolating the effect of each boundary forcing on the climate feedbacks.