Abstract: A preparation method of underfill for flip chip packaging and the device for such method are disclosed. A carrier having a slot at the center thereof is used to hold a substrate having mounted with a plurality of flip chips. The top surface of an upper heat-resistant tape and the bottom surface of a lower heat-resistant tape having the same size are formed into a elongated sealed cavity, and one end of the cavity is injected with fill and the other end is used to extract air so that the underfill is rapidly filled up the cavity between the chips and the substrate, the height of the fillers around the chip can be controlled and will not form bubbles. Thus, the yield and capacity of production are high.