A Laser Doppler Anemometer (LDA) is used to measure and study the flow field in the working chamber of a homogenizer. Flow Patterns, distributions of mean and fluctuating velocities, shear rates are obtained in details. The characteristics of the flow field and the basic principles of homogenizing are presented. These results are very helpful for the improvement of fluid homogenizers. A Laser Doppler Anemometer (LDA) is used to measure and study the flow field in the working chamber of a homogenizer. Flow Patterns, distributions of mean and fluctuating velocities, shear rates are obtained in details. The characteristics of the flow field and the basic principles of homogenizing are presented. These results are very helpful for the improvement of fluid homogenizers.