This paper presented a numerical comparison of the sealing performance between conventional radial rim seal and new-designed honeycomb radial rim seal with three sealing flow rates. Three-dimensional unsteady Reynolds-averaged Navier–Stokes (URANS) equations, coupled with a fully developed shear stress transport (SST) turbulent model from ansys-cfx, were utilized to investigate the sealing effectiveness of rim seal and flow characteristics in the wheel-space of gas turbines. First, the numerical method for analysis the sealing performance of the rim seal was validated on the basis of published experimental data. Pressure distributions on the vane hub, sealing effectiveness distributions on the stator disk surface and swirl ratio distributions in the wheel-space of the experimental models were numerically computed and compared to the experimental data. The additional scalar variable was adopted in calculation to simulate the distribution of tracer gas concentration in experiment. The numerical results were in excellent agreement with experimental data. Then the sealing effectiveness of conventional and new-designed honeycomb radial rim seal are compared. The flow field in the wheel-space of the new-designed honeycomb and conventional turbine radial rim seal was illustrated and analyzed. Furthermore, three cases with different honeycomb cell depths were selected to investigate the influence of honeycomb cell depth on sealing performance of honeycomb radial rim seal. Compared with conventional radial rim seal, the honeycomb radial rim seal could improve the sealing effectiveness by 9–14% at the same sealing flow rate. The honeycomb cell depth has a pronounced effect on sealing performance of honeycomb radial rim seal. It shows that sealing effectiveness of the honeycomb radial rim seal increases with the increase of the honeycomb cell depth, as honeycomb cell depth increases from 1.6 mm to 4.8 mm, the sealing effectiveness is increased by about 8% at most. In addition, the flow pattern of the rim seal and wheel-space is provided to describe sealing flow characteristics.