Historic districts intertwine various elements of historical heritage, cultural significance, social relations and daily activities, and have significant research value. Through a review of previous literature, it can be observed that research on the conservation and renewal of historic districts often focuses on the overall planning and development of macro-level district. Recognizing the scarcity of quantitative studies on spatial morphology at the meso level, this paper introduces a quantitative methodology applicable to historic streets. Utilizing Quanzhou City's West Street Historical and Cultural Neighborhood as a case study, it employs Aspect Ratio (D/H), Interface Density, and Build-To-Line Rate to describe and summarize street interface morphology, presenting transformative strategies for future protection and renewal. West Street's characteristics include: (1) horizontally, influenced by the Tang Dynasty's concept of "lining houses to form streets," it has a high Build-To-Line Rate and density, providing enclosure, limitation, and spatial continuity; (2) vertically, it displays diverse interface morphology with a moderate Aspect Ratio and rhythmic changes, maintaining visitor interest. The study validates the feasibility of this quantitative method and provides valuable insights for the conservation and renewal of historic districts.