Abstract: The CO₂ emissions are mostly from energy utilization. Energy integration not only improves energy utilization efficiency，but also reduces CO₂ emission. This paper introduces a calculation method for the reduction capacity of CO₂ emission through saving energy. In this paper，a case study based on a project of energy integration on a purified terephthalic acid (PTA) plant is presented. The results of the case study indicate that energy integration has significant effect on CO₂ emission reduction.