Using the output data of 47 CMIP6 models and the NCEP/NCAR reanalysis data from 1958 to 2014,this paper studies seasonal variation characteristics of interhemispheric oscillation (IHO) in the model atmosphere,and evaluates the ability of CMIP6 to simulate the seasonal characteristics of IHO.Results show that all 47 CMIP6 models can simulate the seasonal evolution characteristics of IHO,but there are some differences among the models.Through comparison,16 better models for simulating the seasonal cycle of IHO are selected,which can successfully simulate the temporal evolution and spatial structure of hemispheric atmospheric mass.Further analysis shows that water vapor can counteract the seasonal variation of IHO,and the change of water vapor mass in the hemispheres can drive the generation of cross-equatorial mass flow.The surface net short wave radiation is higher in summer and lower in winter,and the water vapor evaporation caused by its heating plays an important role in the change of water vapor mass.The surface net long wave radiation changes greatly in spring and autumn,which is consistent with the monthly change of atmospheric mass.Compared with the reanalysis data,it shows that the peak valley variations of hemispheric atmospheric mass simulated by CMIP6 models have obvious monthly deviations,and the deviations of surface pressure anomalies simulated by CMIP6 models mainly occur in the North Pacific,Eurasia,mid-latitude regions of the Southern Hemisphere and polar areas.There are obvious deviations in the simulated evaporation and precipitation,equatorial wind field,surface net long wave and short wave radiation fluxes in the Northern and Southern Hemispheres.