This article proposes a systematic engineering for sustainable economic and ecologic development. This system is deemed to be applicable in any country of the world. The system aims to realize five important objectives: water source clearance, energy saving and emission reduction, renewable energy and organic fertilizer production, and ecological agriculture development, all in large scale and at low cost. The main conception of the new system to reach these goals is the replacement of the conventional sewage treatment approach with more efficient and more ecological process -the natural fermentation of the mixture of the urban sewage and agrarian wastes, such that water body clearance, including water de-eutrophication, green algae prevention and siltation dredging will all be accomplished at virtually a zero cost. Along with this process, the system can produce a vast amount of renewable energy and organic fertilizers, consequently ecological agriculture development in large scale can be realized. As a result, this system will greatly reduce the use of chemical fertilizers thus largely reduce the consumption of fossil energy and the related polluting emissions. This system is thus fully a circular economy model through full west-reuse processes, which ultimately will enhance our life quality with healthier food and living environment. The system is flexible and adaptable to be implemented in either small towns or megacities. The implementation and operation of this system will also benefits employment growth. Lastly, in terms of economic feasibility and profitability, millions to billions of dollars of annual revenue can be generated from the running of this system in a country.