Photoinduced chemical reactions of 1-butyl-3-methylimidazolium hexafiuorophosphate ([bmim][PF6])were studied by laser photolysis at a wavelength of 266 nm. Excited triplet state 3[bmim]+* was observed, radical cation [bmim] 2+* and neutral [bmim]* radical via photoionization were also formed. Energy transfer from 3[bmim]+* to β-carotene was confirmed. Oxidation via one electron transfer from TMPD to 3[bmim]+* was also observed and the rate constant was determined to be 1.2 × 105 L. mol-1-s-1. The reaction of [bmim][PF6] with hydrated electron (eaq)was confirmed by laser photolysis in aqueous solution.