The quasi-lattice model based on pairwise interactions has been used to study the large deviation from the ideal mixture and the concentration dependent asymmetry in the thermodynamic properties of Mg-Bi liquid alloy. This has been utilised to extract microscopic information such as concentration-concentration structure factor in long wavelength limit [Scc(o)] and warren-cowley short range order parameter a1 of Mg-Bi liquid alloy at 975K. The analysis suggests that heterocoordination leading to the formation of complex Mg3Bi2 is likely to exist in the melt, and is of strongly interacting nature. The theoretical analysis reveals that the pairwise interaction energies between the species depend considerably on temperature and the alloy is chemically more ordered in Mg-rich region of the phase diagram. The alloy behaves like a segregating system in Bi-rich region.