This article presents a systematic methodology for the retrofit of steam power plants in eco-industrial parks, which offers the opportunity of energy integration among companies. Components of this work include the energy reallocation and the retrofitted design of steam systems. In the present study, the current strategy of energy utilization for existing sites is assessed. Retrofit is taken into account to evaluate the potential energy for the integration. The problem is formulated as a mixed integer nonlinear program based on a superstructure approach. The result of an industrial case study shows that the energy integration among plants is benefit, which provides incentive to promote the cooperation of companies in the vicinity.