The thermal parameter model and thermal-mechanical constitutive relationship of recycled aggregate concrete（RAC）are introduced considering the variation of recycled coarse aggregate replacement ratio.The entity unit modeling of RAC filled steel tubular columns is conducted using the finite element software ABAQUS to simulate the mechanical property and fire resistance of such composite columns

and the reasonability of the finite element model is evaluated by comparison with experimental results.Simplified formulae for fire resistance of RAC filled steel tubular columns are further proposed based on various parametric analyses.The results show that:（1）the simulated temperature field and fire resistance of RAC filled steel tubular columns by the finite element model generally agree well with the experimental results

which verify the validity of the proposed thermal parameter model and thermal-mechanical constitutive relationship of RAC;（2）the cross-sectional dimension and slenderness ratio have remarkable effect on the fire resistance of RAC filled steel tubular columns;and（3）the predicted fire resistance using the simplified formulae generally accord well with the experimental results in the literature.