Abstract: In order to investigate the influence of different factors of lubrication system of LR4 A diesel engine, the characteristic of lubrication system and oil pressures in different lubricating galleries of diesel engine were measured on a engine test bed.The results show that the main factors affecting the oil pressure are engine speed, oil temperature, the flow rates of oil pump and PCJ.The pressures of oil galleries in the lubrication system are gradual increased as the speed of diesel engine increases.With the increase of the speed, the oil pressure increases slightly slower in high speed stage.At the same speed, the oil pressures of lubrication system decreases with the increase of temperature.It has a significant effect on the oil pressure increase that increasing the flow rate of the oil pump.Meanwhile, the PCJ with small diameter has an evident effect on the oil pressure increase at low engine speed.