Abstract: The effect of lubricating grease on the fretting wear behaviour of 100C6 steel under different displacement amplitude and normal load has been investigated. Results show that grease lubrication retarded the occurrence of fretting damage, and it is more effective in slip regime than in mixed or in partial slip regime. However, due to the specific movement of fretting, it is very difficult to maintain lubricating grease in the fretted contact surfaces. Compared with dry fretting, no significant difference in the deviding of the fretting regime has been observed with grease lubricated fretting.