The utility model discloses a shock absorption device for a dynamic compaction machine main unit, which comprises a shock absorption cylinder and a shock absorption electric control valve set. One end of the shock absorption cylinder is fixedly connected with a dynamic compaction machine rotary platform, the other end is free, and the shock absorption electric control valve set includes a three-position four-way electromagnetic reversing valve, a two-position two-way electromagnetic reversing valve, an electric proportional overflow valve and a hydraulic lock set, wherein the three-position four-way electromagnetic reversing valve is connected with an oil source, oil ports at two ends of the two-position two-way electromagnetic reversing valve are respectively connected with a rod cavity and a rodless cavity of the shock absorption cylinder, the electric proportional overflow valve is mounted on the rodless cavity side, and the hydraulic lock set is connected with the two cavities of the shock absorption cylinder. The shock absorption device realizes prestress supporting the ground, firm contact between the shock absorption device and the ground is guaranteed, main unit shock impact generated by sudden unloading of the dynamic compaction machine is reduced during operation of the dynamic compaction machine, components of the device are common, cost is lower, safety and reliability are guaranteed, the machine is convenient in electrical control, the prestress can be adjusted according to ground conditions of a construction site, and shock absorption effect of the main unit is increased.