Abstract: Numerical simulation is an effective way to study the hydrodynamics for the industrial scale equipments. In this paper, a mathematical model combined with k ε turbulent equation and multiple reference frame (MFR) was developed to predict the flow field in the crystallizer. The accuracy of the numerical method was validated by comparison with the experimental data of the flow field in a laboratory scale stirred tank measured by partical image velocity (PIV) instrument. Based on the simulation results for the flow field in the crystallizer, the effects of the impeller location, operating parameters on the flow field in the crystallizer were studied in details. It was found that the optimal parameters for the design and operation of the crystallizer were: the installed height of impeller was 1　000 mm, the column length of the crystallizer was 2 000 mm, and the economic rotational speed was 70-80 r/min.