The invention relates to a nuclear reactor fuel assembly bottom nozzle hydraulic scouring test system and a test method thereof. The system comprises: a circulation system composed of a double suction pump and a closed loop pipeline; a test segment module composed of a foreign matter dropping tube segment, a test segment, a foreign matter collector and relevant devices; a flow field information acquisition module composed of a PIV device, flow field processing software and a local area network computer; an image acquisition module composed of a high speed camera and a local area network computer; an adjusting and monitoring module before pump, composed of a water tank, a filter, and relevant pipelines and meters; a cooling module composed of a cooling pump, a cooling tower, a condenser, a closed pipeline, a valve and a meter; and a remote control module composed of all electric valves, water pumps and relevant devices through a programmable logic controller. The invention also provides the test method of the system. The system and the method can meet needs of large-flow reactor bottom nozzle hydraulic scouring visual test researches, and also can realize simple and rapid adjustment of system parameters.