A picosecond pulse radiolysis facility based on a laser-driven photocathode electron accelerator has been constructed. First observation of picosecond dynamics in ionic liquid of DEMMA-TFSI in radiation chemistry was reported. It is found that the electrons produced by ionization are solvated to full solvation in ionic liquid with a rate constant of 3.9 × 10 10 s -1 , and dry electrons before full solvation react rapidly with biphenyl and pyrene with rate constant of 3.8 to 7.9 × 10 11 dm 3 mol -1 s -1 . The geminate ion recombination in n-dodecane and n-hexane was also observed by monitoring transient optical absorption at 523 nm.