Vacuum separation method can acquire low limit water content and coalescence separation method has a high efficiency in lubricating oil dehydration.By combining with the advantages of the two methods,the coalescencevacuum combination separation method of lubricating oil was put forward.The structure principle and working mode of two kinds of separation devices,the coalescencevacuum series combination separation device and coalescencevacuum integration separation device were introduced.By selecting the LTSA46 turbine oil as the text object,the dewatering performance of two kinds of separation devices was tested and compared.The results show that the dewatering performance of two kinds of separation devices is very close,the dehydration efficiency of the coalescencevacuum series combination separation device is slightly higher than that of coalescencevacuum integrated separation device,howerever,the coalescencevacuum series combination separation device has a larger volume,and the vacuum pump needs to work continuously,so the wear is faster