From 2003 to 2013, Macao experienced an economic boom accompanied by rapid socioeconomic development. Macao is a tourist city that depends heavily on an expanding gambling sector, and depends greatly on exogenous resources. In this study, we used H.T. Odum's emergy theory to quantify flows through Macao's urban metabolism and describe the consequences of Macao's urbanization from 2003 to 2013. By employing mass, energy, and emergy metrics, we analyzed different metabolic resources. The anabolic and catabolic flows during urban activities such as importation of resources and discharge of wastes were classified and compiled according to their function in the urban metabolism. Macao's urban metabolism showed different behavior during different periods. The main metabolic factors changed due to changes in the urban structure, government regulations, and other conditions. On an emergy basis, we found that the proportion of the life resource increased as the city developed and expanded. We also found that Macao's anabolic and catabolic density increased, indicating increased metabolic pressure from 2003 to 2013. By analogy with the concept of a biological metabolism, we discuss the criteria and implications of our results for urban metabolism and the consequences for policy makers and urban managers.