The mechanism of intramolecular charge transfer (CT) and the following radiationless dynamics of ofloxacin pharmaceutical product were investigated using femtosecond absorption spectroscopy combined with quantum chemical calculations. The CT and the intersystem crossing (ISC) processes have been established to be the major relaxation pathways responsible for the ultrafast nonradiation of the excited S-1 state. The CT occurs within a time constant of similar to 1.4 ps. The following ISC is determined to be similar to 158 ps and triplet yield can be measured to keep similar to 0.33. Simultaneous, the quantum yields of CT and triplet-triplet state absorption are contributed to be 0.29 and 0.38, respectively.