The internal flow that develops in hydrodynamic coupling is exceedingly complex, especially in incompletely liquid-filled hydrodynamic coupling which contain gas-liquid two phase. For such characterization, particle-image velocimetry (PIV) techniques are now regarded as a powerful tool .To investigate detailed knowledge and distribution characteristic of gas-liquid two phase flow field in hydrodynamic coupling, the PIV measurements are carried on braking condition and rated condition, liquid filled ratio are 50% and 75%. The results help us to understand the more information of flow field in hydrodynamic coupling.