Lithography technology is the core technology of manufacturing integrated circuits. Lithography tools is the core equipment of manufacturing integrated circuits, and illumination system is one of the core components of lithography machine. The working principle of the illumination system of deep ultra-violet step-and-scan projection lithography tools is introduced. The pupil shaping technology, homogenization technology, and polarization illumination technology are reviewed and analyzed. The relevant technical principles and implementation methods are summarized.