In order to improve the gas-fluid mixing efficiency in the stirred vessel, by replacing the solid disc of standard Rushton impeller (RT) with a grid disc, the grid-disc Rushton impeller (RT-G) was designed. Grid independence test was completed. Gas holdup distributions of dual RT were numerically studied by the computational fluid dynamics (CFD) technique and compared with the literature data so as to validate the reliability of the numerical model and simulation method. The same numerical strategy was used to investigate the gas-liquid hydrodynamics of dual RT-G. Results were compared with those of dual RT and it was found that, under the operating condition studied here, dual RT-G had the same double-circulation flow field structure as RT. However, fluid axial velocity around the two RT-G impellers and axial pumping capacity could be enhanced, which contributed to improve the gas distribution state especially in regions adjacent to the impellers, between the upper and lower impeller, as well as in the top area of the stirred vessel. In terms of power consumption, the power number of dual RT-G before gassing was about 5% lower than that of dual RT, which indicated that RT-G was more energy-saving. The relative power demand (RPD) of dual RT-G after gassing was about 8% higher than dual RT, and accordingly was more efficient in gas dispersing.