The global phase diagram or master diagram is constructed for binary mixtures consist of the equal and unequal size of molecules by using the modified van der Waals model. The Griffiths shield region is also presented on the master diagram. The influence of various size differences ratio of molecules on the master diagram is investigated and discussed. It is observed that the GPD are symmetrical around zeta = 0 for the equal-size of molecules and the deterioration in the symmetric behavior of GPD increases as differences of size of molecules increase. From the master diagram, all possible main types of phase behavior for every given interaction energy parameters and various size differences ratio of molecules can be seen directly without long and difficult calculations. (C) 2019 Elsevier B.V. All rights reserved.