Two di-n-butyl dithiocarbamate derivatives were easily synthesized. Their tribological performances as lubricating oil additives in rapeseed oil were evaluated using a four-ball machine, and their chemistry of films was analyzed with X-ray absorption near-edge spectroscopy (XANES). The results indicate that the two compounds possess excellent anti-wear property and good load-carrying capacity. According to the XANES results, for the thermal films, the outer surfaces are mainly composed of N, S-containing polymer and ferric sulfate, and the near-surface and the bulk are composed of ferrous sulfate, while for the anti-wear films, the outer surfaces are only composed of ferric sulfate, but the near-surface and the bulk are mainly composed of ferrous sulfate.