A mining company relocated three of their screw compressors to another spot according to exploitation requirements.After the relocation,the lubricating oil’s temperature of the compressors continued to rise and a lot of black deposits appeared at the oil bank,and the sliding bearing was found broken.The used and new oils,as well as the black deposits were analyzed.The oil analysis results show that the mineral turbine oil used in the compressors can not meet the requirements of hightemperature condition,and the oil is decreased seriously and a lot of oxidation products are generated.In addition,as the environment conditions changed,the compressor load is increased,and the heat generated by friction and compression is increased too,which causes oil temperature rise and accelerates oil oxidation.A synthetic oil with good performance in both high and low temperature was reselected according to the working condition of screw compressors.