With the gradual increase in the total volume of underground commerce in cities, underground commercial spaces are increasingly becoming a key carrier for breaking the constraints of land resources and reconfiguring the relationship between people and land. This paper quantifies and visualizes the layout and scale of underground commercial spaces in the central urban area of Qingdao by using kernel density, multi-distance spatial clustering, and spatial autocorrelation analysis and analyzes the influencing factors by using the geographical detector and MGWR model. The research results show that the underground commercial spaces in the central urban area present a “multi-core–multi-level” layout pattern, and high-density areas are more likely to cluster, with the most significant clustering scale being 3.39 km. Commercial supporting facilities, development of underground space, and population heat value are the core driving factors. The impact of rail transit, centrality, commercial supporting facilities, and development of underground space on the east coast urban area is much greater than that on the west and north urban areas. Finally, corresponding strategies are proposed from the perspectives of business districts, station areas, supply and demand, and planning and management to optimize the development and layout of underground commercial spaces, so as to promote the organic integration of underground commercial spaces and urban spaces.

High-density commercial interchange hubs are important components of transit-oriented urban regeneration. However, high passenger flow does not necessarily generate sustained underground-space vitality. This study examines the Licun high-density commercial interchange hub in Qingdao, China. It explores how amenity supply influences sustainable underground-space vitality through user behavioral responses. Based on 426 valid questionnaire responses, an amenity evaluation system was developed across five dimensions. These dimensions include natural-environment, facility-and-service, consumption-experience, socio-cultural, and transport-connection amenities. The entropy weight method was used to identify the perceptual differentiation of amenity indicators. PLS-SEM was then applied to examine the pathway of “amenity supply–user behavioral response–underground-space vitality.” The results show that natural-environment amenities present the strongest perceptual differentiation, while facility-and-service amenities play a fundamental role in supporting user behavioral responses. Consumption-experience amenities promote visit choice, stay duration, and satisfaction, but may weaken interaction and participation, indicating a potential tension between commercial vitality and public interaction. Transport-connection amenities mainly affect visit choice rather than sustained use. Among user behaviors, stay duration, interaction and participation, and satisfaction feedback are positively associated with underground-space vitality, whereas simple visit choice is not. These findings suggest that sustainable vitality in a high-density commercial interchange hub should not be understood as passenger volume alone. It should be understood as the transformation of transit flow into voluntary stay, interaction, satisfaction, and repeated use. This study contextualizes amenity theory in a high-density commercial interchange hub. It also offers planning implications for underground-space regeneration.