An analytic version of statistical associating fluid theory (SAFT), the so-called SAFT-CP (critical point) equation of state [J. Chen, J.-g. Mi, Fluid Phase Equilib. 186(2001)165-184]. has been developed to predict the second-order thermodynamic derivative properties of n-alkane in the wide density and temperature ranges [A. Maghari, M.S. Sadeghi, Fluid Phase Equilib. 252(2007)152-161]. In this work, we have extended the SAFf-CP model to predict some main derivative properties of binary mixtures of n-alkanes, including speed of sound and heat capacities. The proposed extension is based on the average segment number and shape parameter for a pair in a mixture of hard convex bodies and the classical Lorentz-Berthelot combining rule for segment size and energy is employed. The SAFT-CP model is found to be able to correctly describe the second-order thermodynamic derivative properties as well as pVT properties of binary mixtures studied in this work. (C) 2010 Elsevier B.V. All rights reserved.