tThe conventional UV-based methods for determining the critical micelle concentration (CMC) of surfac-tants often fail for low-solubility surfactants or mixtures of surfactants/solvents or oil dispersants dueto baseline uncertainty of the UV spectra. To overcome the limitations, we proposed and tested a newUV-based approach and found that the surfactant concentration, at which the incipient red shift of thestrongest UV absorbance peak of pyrene occurs, can be used to quickly and roughly locate the range of theCMC for the surfactant. Furthermore, we developed a more robust and accurate method, which can accu-rately pinpoint the CMC graphically by following the change of the maximum measurable peak difference(i.e., the strongest UV absorbance peak minus a weaker reference peak) as a function of the surfactantconcentration. Regardless of the baseline fluctuations, the method was able to accurately determine CMCsof 8 model surfactants and oil dispersants. Based on the UV-absorbance analysis, the ratio of pyrene tosurfactant molecules in micelles was estimated, which further reveals the roles and abilities of varioussurfactants in dissolution/dispersion of pyrene or other PAHs in water. The new method can be used tomeasure CMCs of a wide range of surfactants and oil dispersants.