Abstract: S (2H thiophen 2 yl)methyl N, N dialkyl dithiocarbamates were prepared in laboratory. The extreme pressure, antiwear and friction reducing properties of rapeseed oil with thiophen and S (2H thiophen 2 yl)methyl N,N dialkyl dithiocarbamates as additives and the relationship between the additive structure and triobolgical properties were examined with a four ball machine. The worn surfaces of the steel ball were analyzed by means of X ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). It has been found that thiophen as additive in rapeseed oil worsens the antiwera and extreme pressure properties, while S (2H thiophen 2 yl)methyl N,N dialkyl dithiocarbamates at proper concentrations are effective in improving the antiwear, friction reducing behavior and load carrying capacity of rapeseed oil. The XPS analytical results of the worn steel surfaces indicate that tribochemical reactions were involved for steel steel frictional pair lubricated with rapeseed oil containing S (2H thiophen 2 yl)methyl N,N dialkyl dithiocarbamates as the additives, with the formation of a boundary lubricating and protecting film composed of triester of rapeseed oil and tribochemical reaction products of the lubricants. This contributes to improve the triblogical properties of the rapeseed oil base stock.