Abstract: Large delta impeller is a newly developed pumping-mixing agitator for box- type mixer-settler. It is noted for its longer diameter, big area and simple construction. It has been widely and successfully applied in rare earth metallurgy and other chemical industries.In this work, experiments on some basic hydrodynamics were carried out in comparicon with the case of using Rushton type turbine by laser Doppler and local hydrostatic pressure measurements.It has been found that the large delta impeller has the advantages of higher local velocity and uniform velocity distribution as well as local turbulence strength. It is better than Roshton turbine. Experiment indicates that the liquid drops are mainly dispersed by the turbulence flow stream rather than by the direct impact of the impeller, so that the formation of very fine droplets around the impeller can be avoided and the uniform drop size and its narrow distribution obtained by consuming much lower power.The execllent pumping capacity and the higher driving force of the volumetric flow of his type impeller have been also confirmed by the overall suction head measurements.