Archaeological sites with limited surface visibility and low spatial legibility often depend on presentation systems to communicate historical functions and heritage meaning. Using the Site of Xuanquan Posthouse as a case study, this study examined how visual attention and visitor perceptions jointly inform the interpretive effectiveness of such low-visibility archaeological sites. A complementary two-stage quantitative design was adopted. First, 20 adults viewed 12 static presentation images, and visual attention was compared across eight categories of information. Second, 252 valid questionnaires were analyzed using partial least squares structural equation modeling (PLS-SEM) and importance–performance map analysis (IPMA). Archaeological remains, reconstructed architecture or models, and digital media generally showed shorter time-to-first-fixation values and greater cumulative visual attention, whereas explanatory text, diagrams and maps, and bamboo and wooden slip documents were less visually prominent. Interpretation quality, perceived authenticity, and exhibition experience quality were all positively associated with perceived heritage understanding and perceived interpretation effectiveness, with heritage understanding playing a central mediating role. The findings indicate that effective presentation should connect visually prominent entry points with explanatory, spatial, and evidentiary information so that visitors can progress from recognizing physical remains to understanding their historical functions and heritage significance.