Abstract: The advantages of X-ray magnetic circular dichroism and X-ray magnetic linear dichroism are reviewed. With some typical examples we will show that the techniques based on synchrotron facilities have many advantages, such as elemental specification, high sensitivity, nanometer space resolution, picosecond time resolution, and the capability to measure both ferromagnetic and anti-ferromagentic properties. These techniques are thus very powerful tools in the study of spintronics and its device applications.