In this paper, the tribological behavior of the additive sulfurized olefin on Ni-P brush plating layer was studied systematically on a 'ball-on-disc' testing machine. The composition of lubricating films on wear surfaces was analysed with XPS and AES. It was found that the addition of SO in lubricating oil could increase very much the load carrying capacity and decrease obviously the wear rate of Ni-P plating layer. The chemical reaction film NiS formed by the reaction of SO with Ni-P plating layer on wear surfaces possessed very good anti-scuffing and anti-wear properties.