Abstract: The hydrodynamic lubrication of a newly developed adaptive structure journal bearing with coupling two step films is analyzed theoretically. The flow balance equation is established using an incremental control flow volume to describe the pressure distributions on the variable structure between the coupling two step films. The Reynolds equation and flow balance equation are solved simultaneously by the finite differential method in intercrossing iterative numerical calculations. The influences of operating parameters on the hydrodynamic performances of the bearing such as minimum film thickness, film pressure, load carrying capacity, friction factor, and temperature rise are studied. The results show that the design parameters should be determined rationally to obtain the significant lubrication performance and load carrying characteristics of the bearing.