Abstract: Through analysis the oil leakage reason of the oil pipe joints of hydraulic universal testing machines was confirmed to be that the oil pipe joints produced transversal cracks under action of vibration from the solenoid directional valve, and according that two sets of oil pipe improving programs were established. The first method was increasing wall thickness of the steel oil pipe joints to improve the vibration fatigue resistance of the joints. The second method was using high pressure steel wire braided hose to replace steel oil pipe and changing the connection from rigidity to flexibility to reduce the vibration transmission. The practical operation results show that after improving the test machines ran in good condition and no oil leakage failure recurred. It not only effectively ensured the normal operation of the test machine, but also avoided fuel waste and environmental pollution.