Solid-liquid mixing is a common industrial operation conducted in processes, such as slurry preparation, polymerization, and crystallization. Thus, many studies have investigated the just suspension speed, solid concentration distribution and solid-liquid mass transfer. However, most were done for single impeller systems and few for multi-stage impeller ones. In this study, we examined the suspension of solid particles in a vessel equipped with dual traditional impellers. The combination of the impellers and the optimal installed position were investigated. As a result, it was found that the optimal combination of traditional impellers is one of a pitched paddle pumping down in the lower position and a pitched paddle pumping up in the upper one, and that the optimal clearance of dual impellers is equal to vessel diameter.