Nicotine has been studied for the first time by pulse radiolysis techniques. It has been found that hydrated electron, hydrogen radical, and hydroxyl radical can react on nicotine to produce an anion radical and neutral radical, respectively. Different absorption spectra were obtained, and the related rate constants were determined. The results provide some advices for scientists to study the harmfulness of smoking nicotine to people, which can give some new ideas to make harmless tobacco.