In this study, the liquid liquid equilibrium (LLE) system N1923-Na2MoO4-H2SO4 was investigated. Within different molybdenum concentration ranges, the extraction reactions were determined using the slope method at 293.15 K based on the molybdenum phase diagram. The slopes for Mo(VI) extracted with N1923 were determined as 1 and 4, respectively. Mo(VI) was extracted as H2MoO4 center dot(RNH2) and H6Mo7O24 center dot(RNH2)(4). The thermodynamic models were established with the Pitzer equation for aqueous phase and organic Pitzer as well as Margules equations for organic phase optimized by the General Algebraic Modeling System. Two chemical equilibrium constants and their corresponding interaction parameters were regressed from experimental LLE data. The correlated results were in good agreement with the experimental data. Furthermore, this model can also be used to predict the equilibrium composition and equilibrium pH in the aqueous phase. In addition, the mean ionic activity coefficients for Na2MoO4 and Na6Mo7O24 at 293.15 K were calculated with the Pitzer parameters. The chemical structures of the extraction complex were also proposed to illustrate the association.