With urbanization, not only population is gathering to the city and urban landscape is expanding, but also social structure is changing greatly. At the same time, urban modes of production and consumption are spreading to a wider area. However, with over-concentrated population and extensive expansion of cities, "urban diseases" such as traffic congestion, air pollution, waste accumulation and epidemics occur frequently. City consumes natural resources excessively and discharges a large amount of pollutants to the surrounding environment, which will change the original structure and function of regional ecosystem, and then severe ecological risks emerge and the sustainable development of urban ecosystem is constrained. The ecological risks of urbanization have been gradually getting more attention, but the concrete definition and impacts of urban ecological risks are still unclear. Therefore, this paper defines all kinds of ecological risks and analyses their main influencing factors in the process of urbanization. The major methods for ecological risk identification and assessment are also expounded, and some suggestions for ecological risk management of urbanization are presented.