To achieve the trinity protection goal of “quantity-quality-ecology” for permanent basic farmland and scientifically support the refined governance of territorial space, this paper takes Langxia Town in Jinshan District, Shanghai, as a case study, focusing on the quality evaluation and differentiated management methods of permanent basic farmland at the township scale. Based on multi-source data, including the “Three Zones and Three Lines” delineation results, national land change surveys, and cultivated land quality grades, a comprehensive evaluation system was constructed from five dimensions: intrinsic quality, infrastructure construction, spatial layout, cropping attributes, and protection effectiveness. GIS spatial analysis and statistical methods were employed to quantify the quality differences among permanent basic farmland patches. The study proposes a differentiated management strategy of “prioritizing high-quality areas while utilizing lower-quality ones, and maintaining dynamic balance”. The innovation lies in establishing a multi-dimensional evaluation framework integrating natural endowments, policy implementation, and spatial patterns. This research provides scientific references for the protection, optimization, and major construction project siting of permanent basic farmland in similar regions.