The invention relates to an automatic ink adding machine for a printing ink box and an ink adding method thereof. The automatic ink adding machine comprises a pipeline, a vacuum distributor, a vacuumvalve, an ink measuring pipe, a residue pump can, a residual liquid can, a vacuum pump or compressor which are arranged in a casing, a vacuum watch, a residual ink pump connector, an ink injection connector, an ink box fixture which are arranged at the outside of the casing, an air-gas separator, an ink measuring pump, a display screen, a keyboard, a control unit and an electromagnetic valve including a negative ink injection valve, a first positive pressure valve, a second positive pressure valve and a residual ink pump valve. The automatic ink adding method comprises the following steps: 1.clamping the empty ink box to the fixture; 2. starting the vacuum pump; 3. opening the corresponding electromagnetic valve, and vacuumizing the ink measuring pipe and the ink box; 4. setting the ink application value; 5. opening the ink measuring ink pipe of the corresponding position and pumping the ink to the corresponding ink measuring pipe; 6. determining negative pressure ink adding or positivepressure ink adding and injecting the ink into the empty ink box. The machine and the method of the invention have the advantages of convenient clamping and high ink adding efficiency, thus facilitat ing the management of a plurality of ink adding chain stores, improving the ink adding speed of a soft ink bin and ensuring that the ink box with crazing can be reused.