China has the largest population and the fastest growing economy in the world. The general public's demand for health is rising promptly with the improvement of the living standard. However, the limited and unbalanced medical resource have caused the prominent problem of the society, even in the capital city of Beijing, the new hospital constructions with rational allocation is iminent and significant. Along with the technology development and Internet popularization, GIS approaches and related products has been widely used in the people's daily life. The main focus of this paper is to select a site for building a new hospital in Haidian District of Beijing using GIS-based Multi-Criteria Analysis (MCA). With Analytical Hieraichy Process(AHP) and Rank Order Method (ROM) for the weight setting on factor criteria, necessity tests and sensitivity tests are applied to check which criteria are really necessary and how the results are sensitive to their weight change. The optimal site located in Wenquan Town (E: 116.182, N:40.039) is screened from several candidate sites usin Google Earth maps, which makes the ultimate result more convincing and practical. It can be concluded that GIS-based MCA with necessity and sensitivity tests proposes a novel and useful reference to other site selection decision makers, and also provides constructive tools for the public asministration to set up efficent databases for decision makers to carry out spatial analyses. To make it more maneuverable and practical, a further research on th improvement of this method will have a promising future.