The photochemistry of pyrene in conventional solvents (acetone, acetonitrile, cyclohexane) and ionic liquids ［Bmim］［PF6］, ［BuPy］［BF4］, R4NNTf2 was investigated by time-resolved laser photolytic techniques. The transient absorption spectra of the excited pyrene and other radical species were compared. The absorption band of pyrene cation radical was observed in the acetone, acetronitrile and pyridinium ionic liquid ［BuPy］［BF4］ systems. Only excited triplet pyrene was observed in cyclohexane and ［Bmim］［PF6］ and R4NNTf2. The result demonstrates that there was an interaction between pyrene and solvents, and the pyrene cation radical was formed by electron transfer from the excited state of pyrene to acetonitrile, acetone and ［BuPy］［BF4］. The possible mechanisms of the six systems were suggested.