The author of the study addresses the urgent problem of maintaining the welfare of the urban environment. An integral component for ensuring the comfort of citizens is the stabilization of the ecology of a modern city. The rapid development of megacities and the increase in the proportion of the urban population has a negative impact on the state of the environment. The level of urbanization of cities expanding due to the influx of population is inversely proportional to their ecological state. The aim of the study is to analyze the specifics of modern urbanization, as well as the main environmental problems of large cities. In the process of writing this article, the following research methods were used: analysis of the problems of urbanization and its impact on modern large cities; comparison of urbanization rates in major cities around the world; compilation of data on world urbanization statistics of the United Nations Department of Economic and Social Affairs. Scientific articles and modern scientific works on the ecology of urban systems were analyzed. The main measures for the reorganization of the urban environment were proposed, the implementation of which will help preserve the natural environment and improve the situation of people living in cities.