To investigate the damage level of relative buildings after strong earthquake occurred in Wenchuan, Sichuan province in May 12th 2008, and propose the rational method for strengthening the damaged structures, the damage of buildings was surveyed. Different damages were found in the buildings in the relative regions. Damage types of reinforced concrete buildings mainly included collapse of columns, failure of joints, strong beams and weak columns, failure of infilled wall and partition. Shearing failure was found in the masonry buildings and masonry buildings with reinforced concrete frames on the ground floors. Based on the analysis of damages of these buildings, an idea of retrofitting the damaged building is proposed, i.e., strengthening the damaged members or joints, enhancing the seismic capacity of vulnerability members, and improving the robustness of the structures. According to this idea, the design and construction for more than 200 damaged buildings were conducted.