The transient control equations of 3-D flow in hydrodynamic coupling were coupled calculated by using the methods of large eddy simulation (LES), flow control equation coupled solution, and sliding mesh method for multi-flow regions in CFD software. In order to learn the flow laws of flow field deeply and optimize the structure, the numerical solution of the 3-D flow field has been analyzed. The torque in each impeller of hydrodynamic coupling was figured out based on the numerical solution of the 3-D flow field. Then the characteristic of hydrodynamic coupling was predicted. The prediction characteristic has been compared with the experimental result; it is found that the error between them is less than 7%, which could prove the effectiveness of the numerical simulation method and characteristic prediction. Then the conclusion has been drawn that the numerical simulation method for the flow field of hydrodynamic coupling has applicable value in engineering. 