In the present work, Fe/Ag superlattices were grown by molecular beam epitaxy (MBE) on MgO(001) single crystal substrates maintained at room temperature or at 423 K during the deposition. The structural properties were carried out using small and high angle X-ray diffraction techniques. The magnetic hysteresis loops with the magnetic field applied parallel or perpendicular to the plane of the films were measured by a superconducting quantum interference device (SQUID) magnetometer in the temperature range 5-300 Ii. A comparison of the obtained results showed that the heating of MgO substrates leads to a strong interdiffusion and causes a significant modification of structural and magnetic properties of Fe/Ag superlattices.