Abstarct: Abstract Nowadays, controlling foam structure during the foaming process is an important issue for products with improved properties. The foam behavior is highly dependent on the properties of the interface. A method for improving surface properties and the desired foaming is the usage of natural surfactants. Licorice is one of the plants rich in natural surfactants called saponins. Although extensive studies have been perfomed on the medicinal properties of the extract of this native plant, the surface properties and its effect on the characteristics of foam have been studied to a limited extent. Therefore, in this research, the dynamic surface properties and foam characteristics of licorice root extract have been investigated. In this research, a pendant drop tensiometer device was built with the ability to measure the sinusoidal oscillation of the drop volume with an accuracy of 0.1 microliters so that surface viscoelasticity can also be obtained. The diaphragm method was used for the drop formation mechanism and oscillation of drop volume, unlike common commercial devices. The validation of the pendant drop method was performed by comparing the results of a reliable commercial device and dimensionless numbers investigations. The surface tension results showed that the extract has a high surface activity and can reduce the surface tension by 25 mN/m. Measurements of surface dilatational viscoelasticity were shown that adsorption laxyers are frequency-dependent, so that with increasing oscillation frequency, the surface elasticity increases, while the surface viscosity decreases significantly. Then, the foam characteristics of extract solutions were investigated by Bikerman's method. Foamability and bubble size reduction increase with increasing extract concentration up to the CAC value and then remain almost constant at higher concentrations. Also, the foamability and stability of foams showed a significant correlation with the dynamic surface properties. In addition, in this study, a theoretical model baxsed on dynamics of the flow between bubbles and its validity for drainage of the foam extract, as a measure of stability, was discussed. The comparison between the theoretical and experimental results showed a relatively good agreement for the volume of drained liquid, which can be used to estimate the life of the foam. Also, the relationships obtained in the modeling can be used to quantify the effect of changing effective parameters on foam drainage.