In the context of China's legislation of "ecological civilization", concepts like "ecology", "green" and "low carbon" have become basic requirements for all urban construction projects by the Chinese government. The construction of most new eco-cities is led by local governments. Because of their large scale, long construction period and the investment required, many new eco-cities lack strong financial support from local governments and have to rely on private enterprises. Local governments have shifted the task of solving the environmental problems of the new eco-cities, which are necessary to achieve ecological goals, to private enterprises. Based on the requirements of national policies and the economic interests of private enterprises, these private enterprises had to deal with the contradiction between environmental challenges and economic interests in the early planning stage of new eco-cities. There is relatively little research on private enterprise-led new eco-cities, and there are no suitable working approaches to help private enterprises resolve this contradiction. This paper takes a new eco-city, Zhongshan New City of the developer company China Fortune Land Development (CFLD), as the research object, proposes an Ideal Collaboration Model with the theoretical support of social capital theory. Then, the model is modified by comparing it with the actions of stakeholders in solving environmental problems in practice. The findings show that the modified ideal model can be used as a working approach for solving complex problems, to perfect the process of eco-planning and to facilitate the collaboration of various stakeholders in order to reduce the environmental damage caused by the development of new cities and to avoid future economic losses for the developers. However, public participation seems hard to realize in the early planning stages of the development of new eco-cities.