Lubricating oil system is an important part of compressor unit. The cleanliness of oil pipeline system will directly affect the long period operation of compressor unit. The oil flushing efficiency is directly determined by the quality of lubricating oil, the temporary measures taken in oil flushing stage and the operation means in oil flushing stage. In this paper, some rectification suggestions are given according to the problems emerged during the oil flushing of compressor unit, and the improvement measures are analyzed. The improvement measures are proved effective by the subsequent oil flushing of two refrigeration compressors.