The invention discloses a device for extracting fresh bamboo juice and a method thereof. The device comprises a sleeve, wherein the opening end of the sleeve is fixed to the outer side of one of bamboo joints at the lower part of bamboo by virtue of a sealing fixing sleeve, a hole is formed in the bamboo wall at the upper part of each bamboo joint of the part, located in the sleeve, of the bamboo, the top of the sleeve is provided with an air inlet, and the air inlet is connected with an air compressor through a first pipeline; the bottom of the sleeve is provided with an air outlet, the air outlet is connected to the upper part of a collecting barrel for containing fresh bamboo juice through a second pipeline, and the upper part of the collecting barrel is connected to a vacuum pump through a third pipeline. By performing stage-by-stage pressurization on the inside of the sleeve, air entering the sleeve can enter of the bamboo, and pressurization is continuously applied, so that the internal part and the external part of the bamboo can be pressed jointly, consequently, the fresh bamboo juice of every bamboo joint of the bamboo is squeezed from the bamboo walls and the interior of the bamboo simultaneously to enter the sleeve, and finally, the fresh bamboo juice is extracted through negative pressure, so that the juice yield is high, and the efficiency is high; and the obtained fresh bamboo juice is stored underground, and the temperature is low, so that fresh taste and quality of the fresh bamboo juice are easy to preserve.