The floating ring bearing (FRB) casing usually contains a deep circumferential oil-groove or several axial grooves for the increase of flow rate.However,the existence of the oil grooves complicates the boundary of the oil film.Because the short bearing model is difficult to handle complex boundary conditions and the calculation efficiency of the numerical method is extremely low,two oil film force models,the fluid force database method(FFDM) and the separation of variable method(SVM),were introduced and developed to deal with complex boundary problems of the FRB.Considering the complex boundary introduced by the axial groove,the database of oil-film force and shearing force with three-dimensional structure was established based on FFDM.Considering the complex boundary introduced by the circumferential groove,the analytical expression of the oil-film force was derived based on SVM.The accuracy and efficiency of the proposed methods for FRBs was validated through comparing the numerical results using finite difference method under same conditions.