Abstract: A derivative of benzotriazole containing sulfur and phosphorous was synthesized. The thermal stability of the synthetic derivative was examined with thermogravimetric analysis. The tribological behavior of the derivative as an additive in rapeseed oil was investigated with a four ball machine. The action mechanism of the derivative as an additive in the rapeseed oil was discussed based on X ray photoelectron spectroscopic analysis of the worn surface of the steel ball. As the results, the derivative has fair thermal stability. It as an additive in the rapeseed oil shows excellent load carrying capacity and friction reducing and antiwear ability to some extent. The improved tribological behavior of the base stock in the presence of the derivative as an additive is mainly attributed to the tribochemical action of the active S and P in the additive molecules with the lubricated steel surface. The derivative is a kind of potential environmentally friendly lubricating additive.