This on-line solvent degassing equipment is installed between the mobile phase reservoir and HPLC pump. The mobile phase solvent enters the degasser entry through permeable membrane tube placed in a vacuum chamber. Because of the pressure difference of the wall of the permeable membrane tube, the dissolved gas continuously leaks out of the tube thus causing degassing for the mobile phase solvents. The degassed mobile phase is then moved to HPLC pump entrance through the gas-proof tube.