An ultrahigh-speed bar precision shearing device adopting a type of alternating current servo motors driving a flywheel to spirally compress nitrogen for energy storage includes a frame structure, a high-pressure air chamber mechanism, a hammer head movement mechanism and a mold are installed on the frame structure from top to bottom, the high-pressure air chamber mechanism cooperates with the hammer head movement mechanism to strike the mold, and bars are cut off and separated under the effect of the mold. The present application omits a complex hydraulic driving system, and ultrahigh-speed striking (20-30 m/s) of a hammer head is achieved in a manner of a flywheel spirally compressing nitrogen for energy storage; and control is simple, the return speed of the hammer head is high, and the energy utilization rate is high.