Historic districts carry people's impressions of the city, bear witness to the development process of urban civilization, and are precious heritage of the city. At present, however, the fracture of historical memory, the destruction of architectural styles, the difficulty of cultural inheritance, the lack of social vitality, and the difficulty of adapting the backward environment to modern life have become common problems of historic districts in China. When large-scale development and adjustment are no longer seen as applicable to them, the regeneration of historic districts is challenged. The "urban catalyst" is a theory that originated in the West and then rapidly emerged in China, which aims to activate the original elements in the site without completely changing them, and then, through appropriate guidance, use the linkage reaction between the elements to drive the development and activate the vitality of the whole area.