Abstract: In order to study the water flow characteristics of target layer during the water assisted laser processing, fluid dynamics analysis software FLUENT was used to do the model and simulation of three different flow devices for water assisted laser processing. The velocity field of fluid above target material was analyzed and the results were analyzed in contrast. The results show that, flow field has difference with the difference of device structure based on the analysis of speed-position curves perpendicular to target material. The fluid speed is smooth within the position of less than 1cm above target. The position is good for laser transmission, slag discharge and processing material placement. The study provides a theory basis for building water flow control device of water assisted laser processing.