Abstract: Molecular dynamics simulations combining potentials mapping technique have been performed to investigate the Structure of binary liquid Li-Mg alloys at a constant temperature (924 K). Pair correlation function, bond orientational order and pair analysis approach are adopted to give geometrical descriptions on atom arrangement. The trends of splitting of second-peak in pair correlation function, the orientational order parameters and evolution of various symmetries of bonded pairs, etc., vs composition have been examined. The difference and concordance between the bond-orientational order and pair anaIysis have been first given out. Based on the distribution of attractive part of potentials, it is concluded that the attractive part would dominate the characterization of structure in liquid metals. In addition, icosahedra, defective icosahedra, Frank-Kasper polyhedra and Bernal hole polyhedra formed in liquid Li-Mg alloys are also counted.