The shaping of urban brands from the perspective of art cities has evolved from one-dimensional image promotion to multi-dimensional cultural value construction. With the practice of public art in Jingdezhen as the research object, this article explores how it activates the core driving force of "publicness" and promotes the modernization transition of urban brands from a "millennium porcelain capital" to an "international porcelain valley". Drawing on Habermas' theory of the public sphere and Sandy Lacey's theory of new types of public art, this study constructs a three-dimensional public analysis framework of "space, issue and participation". Combining typical cases such as Tao Xichuan, it systematically analyzes how public art transforms local cultural resources into perceptible, participatory, and communicable brand capital through spatial openness, issue commonality, and participatory publicness. Research has shown that Jingdezhen has established a closed-loop mechanism of "public experience, cultural identity and brand communication" through the public transformation of industrial heritage, the social sculptural transformation of creative markets, and the symbolic translation of local materials, providing a practical path for the branding of culture driven cities with reference significance.