For future climate change under different IPCC emission scenarios, sea level is projected to rise globally. The sea level changes are not going to be geographically uniform, with many regions departing significantly from the global average. Some of regional distributions of sea level changes can be explained by projected changes of ocean density and dynamics. In this study, with 11 available Coupled Model Intercomparison Project Phase 3 (CMIP3) climate models, we identify an asymmetric feature of projected subtropical gyre circulation changes and associated sea level changes between the North and South Pacific, through analysing projected changes of related parameters, such as ocean dynamic height (with reference to 2000 db), depth integrated steric height, Sverdrup stream function, surface wind stress and its curl. Poleward expansion of the subtropical gyres is projected in the upper ocean for both North and South Pacific. Contrastingly, the subtropical gyre circulation is projected to spin down by about 20% in the subsurface North Pacific from the main thermocline around 400 m to at least 2000 m, while the South Pacific subtropical gyre is projected to strengthen by about 25% and expand poleward in the subsurface to at least 2000 m. Such asymmetrical distribution of the projected subtropical gyre circulation changes is directly related to differences in projected changes of temperature and salinity between the North and South Pacific, forced by surface heat and freshwater fluxes, and surface wind stress changes. Above analyses are being repeated with CMIP5 models, preliminary results tend to support above findings in CMIP3 models.