The invention discloses a rapid tamping device and a construction method. The rapid tamping device comprises a tamping plate, lifting plates, reinforcing plates, a positioning cylinder, connecting buckles, bolts, nuts, iron chains, a connecting hammer head and an impact drill. The device is characterized in that exhaust pressure relief holes are machined in the upper half part and the lower half part of the tamping plate, the positioning cylinder is welded to the middle position of the tamping plate, the two reinforcing plates are welded in the longitudinal direction of the tamping plate, thetwo lifting plates are welded in the middle transverse position of the tamping plate, a lifting hole is formed in the middle of each lifting plate, and the connecting buckles and the lifting plates are connected through the lifting holes, the bolts and the nuts; and the iron chains are arranged on the upper parts of the connecting buckles in a matched manner, the other ends of the iron chains aremounted on the impact drill, the connecting hammer head is inserted into the positioning cylinder for positioning, the tamping plate is hoisted through the iron chains on the two sides, and the otherend of the connecting hammer head is connected with a cantilever of an excavator. The rapid tamping device has the advantages of simple structure, convenient operation, strong applicability, no site limitation, high construction efficiency, short construction time, reduced working strength of operators and improved safety.