In order to study the correlation between the stirring power characteristics of ultrafine powder and the operating parameters and the calculation expression of stirring power, the problems of difficult calculation and lengthy calculation time in ultrafine powder stirring simulation were solved. The method of combining experimental research and numerical simulation was used to study the variation law of stirring power and torque of the ultrafine powder mixing process in the mechanical powder mixer. The stirring experiment of light calcium carbonate powder with an average particle size of 10.56 μm was carried out, and the operating parameters in the mechanical powder mixer, including the effects of rotational speed, blade position, and material surface height on the stirring power and torque of ultrafine powder were studied, and the expression of power calculation was obtained. Using the similar principle, the fine particles of the powder were enlarged, and the virtual experiments were carried out on the enlarged coarse particles to obtain the contact parameters. The DEM numerical simulation of the coarse particle stirring process was carried out, and the results of the simulated stirring power and torque were compared with the experimental results. The results showed that the mixing power consumption of ultrafine powder in the mechanical powder mixer was closely related to the parameters of the rotational speed, blade position, material surface height and so on. At the same time, the torque value and power value were positively correlated with rotational speed and material surface height, and negatively correlated with the blade position. The ratios of simulated torque value and power value to experimental torque value and power value were basically consistent with the particle amplification factor, which verified the accuracy of the similar principle applied to study the influence of blade position and material surface height on the stirring power characteristics.