Impurity, such as H2S in light hydrocarbons, usually causes bad odor, corrosion problems, and air pollution after combustion. One of the most effective methods for removing hydrogen sulfide from liquid hydrocarbon streams is a caustic wash process. This process is often applied in the ambient temperature and pressure; therefore, an effective experimental method is carried out in this work to determine the reaction rate parameters in 25 degrees C and 1 atm. Results indicate that the liquid (organic) phase resistance plays the greatest role in the transfer of hydrogen sulfide from hydrocarbon liquid to caustic solution. Moreover, interpretation of the experiment showed that in the ambient temperature and pressure the mass transfer coefficient in the liquid phase is equal to 0.008 S-1.