The quality growth of urban economic growth, which is paid attention to when a city's amount of economic growth develops to a certain stage, is relative to the quantity growth of urban economic growth. As economy develops highly, urbanization is continuously being pushed, and city scale expands unceasingly, the urban economic growth quality is getting more and more attention. Based on the connotation of the economic growth quality, this paper takes Wuxi as an example, and makes empirical analysis on the quantity of Wuxi's economic growth with the PCA. The results show that, Wuxi's economic growth is still mainly focused on the quantity expansion. There are some problems on the potential, constancy, structure, stability of the economic growth, and the usage of resources. By the end, the paper gives some suggestions according to the results of the empirical analysis.