Abstract: The gas-liquid inteffacial area has significant influence on kinetic processes, such as heat transfer, mass transfer and physiochemical reactions in two-phase flow. A new method for getting this parameter is introduced to compute the inteffacial area with the numerical simulation results of two-phase flow. Referring to the idea of a piecewise linear interface calculation (PLIC) method, it uses a plane in each cell to approximate the real curved interface between two phases, these planes are then categorized into five types according to the volume fractions of the target fluid and their gradient vectors in each cell, and the inteffacial areas are respectively calculated by different equations for different plane types. This method is applied in analyzing the numerical simulation results of a copper converter. It is shown that this method can extract the interfacial area of any spatial region effectively in a two-phase flow system and can be used in analyzing the features of kinetic processes quantitatively in a two-phase dispersion system. Moreover, by using the computed interfacial area, the oxygen utilization ratio is calculated and the "highly efficient reaction zone" in the bath is recognized. The results agree with practical data and experience, indicating the accuracy of the proposed method in some extent.