Selection of the appropriate shield machine to fit complex layers and construction requirements is critical for shield crossing projects while it is finished qualitatively according to construction experience at present. The paper presents that the fuzzy analytical hierarchy process (FAHP) and the optimum selection of shield is done in terms of qualitative evaluation and quantitative calculation by 3 steps which include establishing the hierarchical model, determining the fuzzy consistent matrix and calculating index weights. The successful application of FAHP in Yangtze River shield crossing project in Yichang shows that the essential part of FAHP is the establishment of hierarchical model. The comprehensive index weight whose value has no real physical meaning is only used for comparing and sorting.