Two kinds of aero-engine cylindrical intershaft bearings are analyzed with quasi-static method

in which one has co-rotating inner ring and outer ring

and the other is counter-rotating.Their cage's speeds and rollers' speeds under different radial loads are discussed

and then their operating performances are compared.It is concluded that

when the intershaft bearing is counter-rotating and its inner ring's speed is larger than its outer ring's

it has lower cage slip rate and longer fatigue life

and is helpful to wear and vibration stability of rotor system;when the bearing is co-rotating and its inner ring's speed is smaller

its speeds of rollers in the loaded zone are lower

and it benefits the life of rollers.