The impeller of submersible mixer in some sewage treatment plant, whose parts are imported from other countries, is heavily abased. To solve this problem and realize domestic manufacture, based on reverse engineering theory, utilizing 3 coordinates measuring machine and applications of Surface and Pro/E, 3D solid model of impeller are gained. The gained impeller model accords with the physical one with high accuracy. The flow formulation is founded as console formulation first, and with the body-fitted coordinate system and standard turbulent model, the numerical simulation of the internal 3-D incompressible turbulent flow agitated flow field of submersible mixer is carried out by numerical simulation software Fluent. The results showed that: the mixer impeller produced vortex jet flow, the constant velocity lines advanced as ellipse, the velocity along the centerline are larger than others, and utilized volume flow to transport the liquid.