The invention relates to an under-pressure feeding vibration-reducing device, which comprises a catalyst feeding assembly, a raw material feeding assembly, a dilute alkali feeding assembly and a reaction kettle, wherein a mixed medium obtained after the mixing of a catalyst supplied by the catalyst feeding assembly and a raw material supplied by the raw material feeding assembly is supplied to thereaction kettle, the dilute alkali feeding assembly supplies a dilute alkali to the reaction kettle, the catalyst feeding assembly comprises a catalyst metering tank, a diaphragm pump and a first damper, the raw material feeding assembly comprises a plunger pump, a raw material metering tank, a centrifugal pump, a second damper, a safety valve, a third damper and a fourth damper, and the dilute alkali feeding assembly comprises a dilute alkali tank, a metering pump and a fifth damper. The invention further discloses a sugar alcohol production line using the under-pressure feeding vibration-reducing device. According to the invention, the pressure is balanced and buffered by using the dampers to reduce the vibration caused by high pressure, especially instantaneous high pressure; and the failure rate of equipment is reduced by 70-80% by using the under-pressure feeding vibration-reducing device.