Land subsidence has caused catastrophic damages to urban infrastructures in mega-cities. This paper uses trapezoidal fuzzy numbers (TFN) combined with Analytical Hierarchy Process (AHP) for ranking the assessment indices of land subsidence induced risk in Shanghai, China. For this purpose, the assessment structure for land subsidence induced risk is established on the basis of trapezoidal fuzzy AHP (Tr-AHP). Subsequently, the latter method is used to calculate the weight of each assessment index. The results show that, for the hazard index, land subsidence intensity yields the largest weight; while for the vulnerability index, the highest weight corresponds to the population density. The method applied in this paper provides a valuable reference for the risk assessment of land subsidence in mega-cities.