The perspective of strong/weak sustainability has a great impact on sustainability assessment. In this study, two most widely used indices, Ecological Footprint (EF) and Genuine Progress Indicator (GPI) for strong and weak sustainability assessment, were employed to evaluate the sustainability of China’s ten megacities between 1978 and 2015. The results showed that the ecological footprint had been enlarged in the past twenty years; while the genuine economic welfare started to increase since 2005. The cities of Xi’an, Chengdu, Chongqing, and Shanghai met the threshold of below 2.5 global hectares for EF/capita, and over 3000 dollars/capita (in 2010 US for GPI/capita. By analyzing and comparing the characteristics, the processes and results, and the complementary features of evaluation methods of EF and GPI, the research suggested that: (1) Strong and weak sustainability indicators, with their own pros/cons in sustainability assessment, should be used carefully; (2) Weak sustainability indicators could be analyzed from the perspective of strong sustainability; (3) Strong sustainability indicators need to be developed urgently. The results in this study could guide the selection of sustainability indicators, and help interpret the results of sustainability assessment.
