Pulsed laser deposition method was employed to grow MgO thin films with preferred orientation on bare Si(100) and SiO₂/Si(100) substrates. The orientation of MgO thin films was systematically investigated by varying deposition parameters. XRD analysis showed that the preferred orientation of MgO thin films would change from (111) to (100) when laser fluence decreased and oxygen pressure increased to certain extend. But it was difficult to fabricate completely (100)-oriented MgO films. Substrate temperature seemed to have little influence on the orientation of MgO thin films at high laser fluence. SEM images of the MgO thin films on Si(100) deposited at 400°C and the laser fluence of 5J/cm² in the oxygen ambient of 200mTorr demonstrated that there was no presence of interfacial reactions or cracks and the film surface was very smooth. Such film is suitable as buffer layers for the growth of high-quality ferroelectric and superconducting overlayers.Singapore-MIT Alliance (SMA)