Public space plays a pivotal role in translating language policy into real-world practice. This study is grounded in empirical data collected through ethnographic fieldwork and semi-structured interviews from the Beijing Subway Line 1, which is typical of the normativity of a public space. The findings indicate that the linguistic landscape (LL) serves as a tangible representation of the inherent normativity within the subway space. Language policy implemented in the subway LL is achieved through hierarchical, process and result intervention. Hierarchical intervention addresses the synchronic stratification of normativity represented by the subway LL and its evolving connotation over time. Regarding process intervention, the subway LL utilizes two approaches to express normativity: the unity of semiotic features and indirect speech acts. Result intervention means that passengers perceive the normative representations of LL as knowledge and transform "de facto" language policies into experience. These intervention methods illuminate the intricate mechanism of language policy embedding in the normative representation of the LL within subway space. The harmonization of language policy with the LL, subway space, and passenger behavior collectively shapes the subway into a vital transportation hub.