Being hives of intensive industrial activities, industrial parks become the focus of water pollution control. However, water management at industrial levels is a challenging job because of the diversification of industrial types, complexity of wastewater treatment network, and interactive metabolism of various elements. Industrial metabolism, especially for phosphorus and nitrogen, can present insights for improving water use efficiency and reducing water pollution. Based on previous research of phosphorus metabolism, this paper established a hierarchical nitrogen metabolism framework for industrial parks, by applying substance flow analysis methods. Firstly, a metabolic network was established at the level of the entire park, comprising the resource systems, environmental systems, and the park′s internal and external socio-economic systems. The park′s internal socio-economic systems comprise nitrogen conversion modules and treatment modules. Nitrogen conversion modules contain transportation, industrial systems, domestic sources and ecological process. Nitrogen treatment modules contain water treatment which include pre-processing facilities of enterprises and wastewater plants, and solid waste treatment which include incineration, landfill and hazardous waste treatment. Then, more detailed metabolic networks were delineated for industrial systems and wastewater treatment systems. Industrial systems further divide into six industrial types: heating and power plant, nitrogen fertilizer production, chemical industry, printing and dyeing, food processing, and other industries. Wastewater treatment systems further divided into physical treatment and biochemical treatment. Based on the network topology, the metabolic structure and dynamic mechanism were analyzed to seek measures for improving water use efficiency and reducing water pollution. The case study on the Yixing Economic Development Zone showed the following: a) compared to phosphorus flow systems, nitrogen flow systems contain more modules, and also the flow is much greater and centralized; b) nitrogen fertilizer production, printing and dyeing and food processing, were major water nitrogen-emission industries, accounting for 96.5% of total industrial water nitrogen-generation of the entire park, though however, wastewater of these industries goes through efficient treatment processes; c) opposed to phosphorus treatment, wastewater plants had a lower (about 57%) nitrogen removal ratio than pre-processing facilities of enterprises (about 79%), because of design and operation problems; d) most enterprises of the park have only simple wastewater pre-processing facilities (physical treatment), which can only remove 6% of the nitrogen, and about 56t water nitrogen-generation of the park goes directly into the water bodies just after simple pre-processing; e) untreated precipitation into water bodies causes a high pollution load in water bodies (around 28%), because of the low management ratio of domestic waste and solid waste of enterprises; and f) domestic sewage has low nitrogen removal ratio (about 54%), due to the simple pre-processing of enterprises. Following these results and further discussion, some suggestions were put forth: a) simple wastewater pre-processing and wastewater plant should be improved for higher nitrogen removal ratio; b) wastewater pipeline system of the park should be improved to let more enterprises′ wastewater, especially more domestic sewage be treated by the centralized wastewater treatment plant; and c) domestic waste and industrial solid waste of enterprises should be well managed and treated to avoid nitrogen going directly into water body through precipitation.