We report on the structure study of MgxZn1-xO films and, in particular, we will focus on MgxZn1-xO layers with x=0.28 and 0.41 MgxZn1-xO layers with different crystal structures of cubic and wurtzite that have been grown by plasma-assisted molecular-beam epitaxy on MgO/c-sapphire with Mg/Zn flux ratio control. The MgxZn1-xO films have been characterized by high-resolution transmission electron microscopy (HRTEM) and high-resolution x-ray diffraction. The dependence of the cation-anion bond length to Mg content has been studied. A virtual crystal model of MgZnO has been applied to interpret the bond-length variation. HRTEM results indicate that the initial stage of the MgZnO growth on a MgO buffer layer starts with a cubic structure even in the case of a wurtzite structure at the end of growth.