The new “I” type double-decker ball bearing (NITDDBB) with two inner contact ball bearings is proposed to improve the speed and load capability of the original I type double-decker ball bearing (OITDDBB). Based on the quasi-statics principle, the mechanical model of the NITDDBB is established and takes into consideration the radial load, axial load, and ball centrifugal forces, as well as the gyroscopic moments. The corresponding calculation model is established on the matlab platform. The mechanical characteristics of the NITDDBB are analyzed and compared with the OITDDBB and also with a single-decker ball bearing (SDBB). Finally, a bearing load test rig is designed and built to verify the simulation results. The results provide a theoretical and experimental basis for the application of the NITDDBB.