Using the observed sea surface temperature data of the Hadley Center， as well as the model data under historical experiments in the Coupled Model Intercomparison Project Phase 5 （CMIP5） and the Coupled Model Intercomparison Project Phase 6 （CMIP6）， the simulation ability of the two most important interdecadal scale modes， the Atlantic Multi-decadal Oscillation （AMO） and the Pacific Decadal Oscillation （PDO）， in CMIP5 and CMIP6 was analyzed and evaluated. By comparing the multi-model ensemble， it is found that in terms of spatial patterns， both CMIP6 and CMIP5 can simulate the signals of AMO in the North Atlantic region， but the simulation of CMIP6 is better. For PDO modes， both can simulate the signal in the North Pacific region， while for the PDO signal in the tropical Pacific region， the amplitude of the CMIP6 simulation is significantly closer to the observation. In terms of periodic simulation， the results of CMIP5 and CMIP6 are similar， and both can simulate the 60~70-year period of the AMO and the double periods， namely 20 and 60~70 years， of the PDO. On the whole， CMIP6 has a certain improvement in the simulation of spatial characteristics compared with CMIP5. But there is no significant improvement in the ability of periodic simulation.