The invention relates to a system for continuously hydrolyzing hemicellulose to prepare a xylose liquid. The system comprises a neutralization unit, an acid regulating unit, a feeding unit, a liquidation jet unit, a feeding and discharging heat exchange unit and a discharging control unit, wherein the neutralization unit comprises a raw material tank, a neutralizing concentrated sulfuric acid pumpand a neutralizing pipeline mixer, the acid regulating unit comprises an acid-regulating concentrated sulfuric acid pump, an acid-regulating pipeline mixer and an acid regulating tank, the feeding unit comprises a feeding tank, the liquidation jet unit comprises a liquidation injector and a liquidation maintainer, the feeding and discharging heat exchange unit comprises a feeding and dischargingplate type heat exchanger and a first discharging temperature sensor, and the discharging control unit comprises a discharging valve and a reflux valve. The prepared xylose liquid exchanges heat witha hemicellulose liquid in the feeding and discharging plate type heat exchanger, so that the temperature of the xylose liquid is reduced, and the temperature of the hemicellulose liquid is increased.The invention also discloses a method for using the system. The system for continuously hydrolyzing the hemicellulose to prepare the xylose liquid has the advantages that heat exchanging is performedon feeding and discharging simultaneously, thereby greatly reducing the energy consumption; feeding and discharging are performed continuously, thereby improving the production efficiency, and simplifying the workers' operation.