The utility model relates to a sand box pre -compaction device, including I -steel top beam, I -steel bottom crossbeam, I -steel pillar, the welding of I -steel pillar is at the both ends of I -steel top beam crossbeam bottom the I -steel, and I -steel top beam below is equipped with the jack, and I -steel bottom crossbeam top is equipped with the sand box, and I -steel top beam both sides are equipped with fixed pendant no. 1, and the jack both sides are equipped with fixes pendant no. 2, and fixed pendant no. 1 and fixed pendant are equipped with chain block, concrete implementation steps between two: use chain block to hang upside down the jack in I -steel top beam, use chain block arranges the sand box of pressurized in on the crossbeam of I -steel bottom, the sand box height is got to the volume, calculates roof beam body construction load, equallys divide the sand box equally, calculates the sand box atress, open the oil pump and carry out the pre -compaction, reach the pressure -bearing design value, the utility model discloses make the sand box reach design pressurized value, reduced the settling amount in the work progress, guaranteed spike bottom gap, improved work efficiency.