Superconductivity represents a magic macroscopic quantum phenomenon. There have been two major categories of superconductors: the conventional superconductors represented by metals or alloys; and the unconventional superconductors represented by cuprates and iron-based high-temperature superconductors. While the superconductivity mechanism of the conventional superconductors is successfully addressed by the BCS theory of superconductivity, no consensus has been reached in understanding the high temperature superconductivity mechanism for more than 30 years, which has become one of the most prominent issues in condensed matter physics. Revealing the microscopic electronic structure of unconventional superconductors is the prerequisite and foundation in understanding their superconductivity. Angle resolved photoelectron spectroscopy (ARPES) plays an important role in the study of unconventional superconductors because it can directly measure the electronic structure of materials. In this paper, our recent progress in the ARPES study of electronic structure and superconductivity mechanism of high temperature cuprate superconductors and iron-based superconductors is reviewed. It mainly includes the electronic structure of the parent compound, the non-Fermi liquid behavior in the normal state, the band and gap structure of the superconducting state, and the many-body interactions both in the normal and superconducting states. These results will provide important information in understanding the superconductivity mechanism of Cu-based and Fe-based superconductors.