Matching problem of submersible mixer and pool has been a difficult problem. Based on in-depth study of the flow field characteristics of a submersible mixer, combined with fluid mechanics theory, the matching problem is discussed in this paper. Calculation formulas of the axial advance distance and effective stirring radius are obtained; meanwhile the critical dimension of matched pool is proposed: length × width × height = V 0.3 × 2 1 V 0.3 × 2 2 V 0.3 , and calculation formula of the critical impeller diameter critical is obtained. They are theoretical foundation of matching criterion between pool and submersible mixer. Matching relationship of pool and submersible mixer is widely used in engineering practice with the help of experiment and CFD numerical simulation, and it can provide significant help for the selection of a submersible mixer.