The atomic structure of quasicrystals has always been a confusing problem, especially for the position of light metal atoms.In this paper, we present a molecular dynamics simulation on quasilattice with particular quasiperiodie boundary condition.Exemplified with the study of atomic structure of decagonal Al-Co-Ni, we find that the atoms on the same layer energetically prefer to occupy the vertices of a tiling constructed by triangle and rectangle tiles, while all the vertices of the tiling locate in the middle of tiles on adjacent layer.We propose an atomic model of Al-Co-Ni quasicrystal with most atoms obeying the rules we presented, though some defects inevitably accompanied when making it meet Penrose tile on the large scale.