A continuous bubble-column scrubber, capturing CO 2 gas by monoethanolamine (MEA) solution in a pH-stat operation, is used to search for optimum process parameters by means of the Taguchi method. The process variables are the pH of the solution, gas flow rate, concentration of CO 2 gas, and temperature. From the measured outlet CO 2 gas concentrations, the absorption rate and overall mass transfer coefficient can be determined with the support of a steady-state material balance equation as well as a two-film model. According to the signal-to-noise ratio, the significance sequence influencing the parameters and optimum conditions can be determined. CO 2 concentration and pH value proved to be decisive parameters, while temperature and gas flow rate were minor. Five sets of optimum conditions were obtained and could be further verified by empirical equations.