Cities and Urban centers are hot beds for future innovation in the field of energy efficiency. At present, energy use in cities accounts for more than 60% of total world energy use and this trend is expected to increase with the growth in urbanization in various parts of the world. The role of Ecocities in this regard is of considerable importance.This paper discusses a model that was developed to assist the target setting in the planning process of an Ecocity in China. The Ecocity located in the Wuxi region in China, is currently in its planning stage. The model has been developed with a systems thinking approach, using STELLA. Different sectors comprising the Ecocity i.e. built environment, transport, water and waste management and energy generation have been considered. An effort has been made to take into account various possible synergies and feedbacks in the system that can be utilized to improve the performance of the overall system. An interactive interface has been provided to help different stakeholders in the decision making process. A participatory approach was adopted in the development of the model where different key parameters were identified as a result of a collaborative exercise with the various stakeholders. A framework for Participatory Modeling and Simulation has been developed. The model gives a possibility to visualize the energy saving potential for different technologies being proposed for implementation in the eco-city. Different scenarios have been created in conjunction with the identified sectors to reflect various levels of ambition towards energy saving in the eco-city.