An effective scaling system must possess suitable application characteristics and internal structures. All types of scaling methods have order-preserving properties. Statistical analysis of safety accidents demonstrates the following: The contribution rate of influence factors of the criterion layer to the target layer does not differ significantly, the strength of the nature is similar, and the 1-9 scale is not conducive in accurately expressing the relative significance of each element. Even though we can use a scale of 1-9, the judgment matrix fails to objectively reflect the judgment of decision makers, resulting in the distortion of decision results and reduced credibility. Guo P et al. [13] proposed another fractional scale method (5 /5, 5. 5 /4. 5, 6 /4, 6. 5 /3. 5, 8. 5 /1. 5, 9 /1) and provided their RI results. Compared with the 1–9 scale, it is more reasonable when the nature and strength of influencing factors are similar. Because the 1–9 scale has an effective uniformity, perceptibility, and memorability, it is advantageous to use the 1–9 scale when there are differences in the properties and intensities of the factors affecting the index layer. Combined with the characteristics of construction projects, the criterion layer adopts the 5/5–9/1 scale method to construct the judgment matrix. The index layer adopts the 1–9 scale method to construct the judgment matrix. The relatively crucial criteria are listed in Tables 3 and 4.