This paper presents a numerical comparison of sealing performance between conventional radial rim seal and seven different kinds of groove radial rim seal with three coolant 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, are utilized to investigate the sealing effectiveness of rim seal and flow characteristics in the wheel-space cavity of gas turbines. The numerical method for the pressure distributions on the vane hub and sealing effectiveness of rim seal is validated on the basis of published experimental data. The seven kinds of groove rim seals designed in this work include four circumferential groove structures, one axial groove structure and two oblique groove structures. The sealing effectiveness of conventional and seven different groove rim seals are compared. Then the flow field in the disc cavity of conventional and groove rim seals is simulated and analyzed. Compared with conventional radial rim seal, the groove rim seals can increase the sealing effectiveness obviously. It is shown that the groove structures improve the damping dissipation of invading gas. The number of grooves has an obvious effect on sealing effectiveness of circumferential groove rim seals. The axial groove case results in less minimum sealing flow rate than oblique groove cases. In addition, the flow pattern of rim seal and disc cavity is used to describe rim seal gas ingestion flow characteristics.