Endurance and reliability of an aeroengine and its bearings are closely related to the thermal state of thebearing oil cavity.The major heat sources which affect the thermal behavior of the bearing oil cavity in an aeroengine are analysed.The models for calculating bearing heat generation,graphite seal heat generation,heat leaking from the graphite seal,convection coefficients and temperature fields of the bearing oil cavity are established.The thermal balance coupled equations of the bearing oil cavity are derived from these models by thermal net method and are solved by quasi-Newtonian method.The steady state temperature fields of the bearing oil cavity are obtained from the solutions of 10 different operation conditions and are consistent with the experimental results in general.