Abstract: A technique for measuring dynamic surface tensions, which is based on the theoretical analysis on a growing bubble, is proposed. The growing process of the bubble is captured by video-image technique. An edge-tracing algorithm using a local threshold and profile optimization is applied to determining the shape of the growing bubble. A device for measuring the dynamic surface tension from the profile of a growing bubble is set up, so that the dynamic surface tension can be determined directly as a function of time. The dynamic surface tensions of sodium dodecyl sulfate (SDS) solutions are also measured.