Agitators are mainly used for the preparation of the drilling and workover fluids and chemicals on offshore oil platforms. In recent years, the methods to improve the mixing efficiency are mainly limited to the optimization of the blade shape and transmission efficiency, but with few reports about the improvement in the driving mode and the mixing principle. In view of the above problems, a mixing agitator is proposed that uses pressure gas as the power to drive the agitator for two kinds of agitation: mechanical agitation and gas agitation. The mixing flow field is numerically simulated by the computational fluid dynamics (CFD) and tested by the Laser Doppler Velocimeter (LDV). The results are compared and analyzed with those of the conventional agitator. It shows that the velocity distribution above the blades of the new agitator is relatively uniform, and there are fewer low-speed areas under the agitation of bubbles, forming a stable turbulent flow. In the region below the blades, better agitation is found on the two ribs with a wider range of action for the new agitator. The new gas-driven agitator has good research and application value.