Interfacial Heat and Mass Transfer Are Prevalent in Industrial Processes. the Interfacial Transfer Rate Can Be Obtained by the Product of their Fluxes and Interfacial Area Concentration (IAC) Calculated by the Interfacial Area Transport Equation (IATE). Bubbles Show Different Behavior According to their Sizes. Hence, Bubbles Are Classified into Two Groups. Consequently, Two-Group IATE is Required Causing to Use of Two Gas Momentum Equations Leading to More Complexity. the Present Study Suggests a New Reliable Two-Group Drift-Flux Modeling to Reduce the Two Gas Momentum Equations to One Gas Mixture Momentum Equation for Gas-Liquid Flow in Large-Diameter Pipes. the Model is Developed based on the Drift-Flux Model Concept and Experimental Data. Group-One and Group-Two Distribution Parameters and Drift Velocities Are Validated through Experimental Data. the Results Show that the Proposed Two-Group Drift-Flux Model Can Support the Concept of Drift Velocity from the Bubbly to Beyond the Bubbly Flow and Consistency between the One-Group and Two-Group Drift-Flux Models. Moreover, Steam-Water Data Are Used to Validate the Applicability of the Model in Steam-Water Flows Condition. the Developed Two-Group Drift-Flux Model is Indispensable for Reducing the Two Gas Momentum Equations to One Gas Mixture Momentum Equation When Two-Group IATE is Implemented into Thermal-Hydraulic Codes to Improve the Prediction Accuracy of IAC.