In order to make the switch valve in abrasive-liquid device of premixed abrasive water jet cutting system work normally, the sealing bush which ensures the pressure constant and the switch smooth is needed. The structure, material and craft of the switch valve sealing bush are studied in this paper. The different weight content of short glass fiber reinforced nylon is tested in the environment of no lubricant, water lubricant and oil lubricant. The result shows that in oil lubricant environment, the 33% weight content of short glass fiber reinforced nylon composites have the best capabilities and the least resistance of friction. The experimental result proves that the sealing bush made by the prepared short glass fiber reinforced nylon composites can meet the require of the premixed abrasive water jet cutting system, according to which the sealing bush is producted and assembled to the abrasive-liquid device.