Abstract: Rapid urbanization in China has led to the continuing expansion of urban space and population, causing growing problems of urban traffic congestion, environmental pollution and increasingly scarce land resources. Since urban underground space is an important part of urban resources, proper development of underground cities may alleviate these problems to some extent. In this report, we briefly described the current status of urban underground space development and utilization in China and the types of urban underground space applications, and analyzed the characteristics of the internal environment of underground space such as constant temperature, heat insulation, high humidity, poor air circulation, insufficient natural lighting, lack of natural landscape and ecological support, etc. Taking the Xi'an SAGA International Shopping Center as an example, we then summarized the key concepts and procedures in underground complex interior design using natural and artificial lighting, plant water and interface design. Finally, we proposed the following optimization ideas on urban underground commercial space interior design: (1) Design clear spatial layout that conforms to human spatial cognition habit; (2) Introduce natural lighting through entrance expansion or modern technology; (3) Use artificial lighting that simulates natural lighting; (4) Introduce natural elements to achieve natural transition between indoor and outdoor environments and create open and vibrant underground space to alleviate human psychological and physiological barriers; (5) Design variable dimensions of underground space conforming to human scale to avoid discomfort; (6) Pay attention to people of reduced mobility and set up no-barrier access ways; (7) Set up ample rest areas; and (8) Encourage local design ideas to reflect regional cultural characteristics.

Key words: urban underground space, environmental characteristics, interior design, Xi'an SAGA International Shopping Center