This paper uses self-association model to compute the concentration dependence of free energy of mixing (ðºð??), activity (a), and the microscopic properties such as concentration fluctuation in the long wavelength limit (ð??ð?ð?), and Warren-Cowley short range order parameter (ð?¼1) for Sn-Zn binary liquid alloy. The calculation reveals the homo-coordination or phase separation at all concentrations with moderate interaction for Sn-Zn liquid alloy at 750 K.