As a pre-work for real time control of dye adsorption in acid dye/nylon system, a dyebath pH control system was developed by combining chemical dosing and pH measuring equipment, dye bath analysis system, and pH control software. Three types of pH control profiles (Gaussian, exponential, and linear) were proposed for control of dyebath pH and dyeing rate. pH control results were estimated at various conditions-acid and alkali concentration, flow rate of dyeing bath, acid and alkali feed interval. The relation between the pH control profiles and adsorption behaviors of the dye was discussed. From these results, it was concluded that the Gauss type profile was more appropriate than other types for the dyebath pH control in nylon dyeing with acid dyes.