Mg x Zn 1−x O thin films were deposited on fused quartz substrate by PLD method with Mg 0.4 Zn 0.6 O source target, and the effect of the substrate surface atom constitution and the migration characteristics of reactive atoms on crystal structure of the MgZnO thin films were studied. Under oxygen-deficient condition, Mg x Zn 1−x O thin film deposited mainly along (200) orientation of cubic structure lattice at temperature below 350 °C because of the alternatively constituted substrate surface by Si and O atoms and the weak horizontal migration of reactive atoms, mix-constituted substrate surface(Si/O areas and O-rich areas) and the intense horizontal migration of reactive atoms introduced phase separation in Mg x Zn 1−x O thin films deposited at higher temperature. Single cubic structure (200) Mg 0.38 Zn 0.62 O thin films was made at 300 °C with Zn composition over theoretical limit in bulk materials, the band gap of which reached 4.2 eV and the MgZnO thin film could detect 330 nm near-UV light. And the available UV range of the cubic Mg x Zn 1−x O thin film deposited at 350 °C was widened to 348 nm near-UV light because of the cubic MgZnO grains with even higher Mg composition in this sample. Under high temperature and oxygen flow rate condition, Mg x Zn 1−x O thin film deposited mainly along the (200) orientation of cubic structure lattice at 2 Pa pressure, Mg x Zn 1−x O thin film deposited mainly along the (111) orientation of cubic structure lattice on O-rich substrate surface when the migration energy of reactive atoms is extremely small at 10 Pa oxygen pressure, and both mixconstituted substrate surface and medium migration energy of reactive atoms cause the phase separation occurred in Mg x Zn 1−x O thin films deposited under medium oxygen pressure. On the basis of the different substrate surface atom constitution and different migration characteristics of reactive atoms considering particular deposition method and condition, some previous results on the formation of different structure Mg x Zn 1−x O thin films and phase separation could also be interpreted. So the available UV range of cubic MgZnO thin film could be adjusted widely from near-UV (348 nm) to vacuum UV (<200 nm) range when both substrate surface atom constitution and migration characteristics of reactive atoms are suitable under given condition by multiple methods.