Abstract: The origin of light and electron is a very fundamental issue in physics, and the activities for searching the answers have spanned almost in the whole history of physics.Starting from the corpuscular theory of light,the author explains why the wave theory can be successfully used to understand the light phenomena of refraction and interference.On the basis of the transverse property of light, the author further discusses the possibility of existence of a special medium,whose vibration corresponds to the light wave.After establishing the relationship of electricity and magnetic field, Maxwell pointed out that light is a kind of electromagnetic wave.According to the emergent principle of condensed matter physics,the author illustrated that it is the vibrations of the string density wave in a string-net liquid that correspond to the electromagnetic wave,and it is the ends of strings that correspond to electrons.A unified theory can be developed for the origin of light and electron.