According to the requirement of Chinese National Policy of energy efficiency and emission reduction, optimized retrofit on the air-conditioning system of existing building is not only a measure to improve the building energy efficiency but also an important part to implement the emission reduction. This article put forward pertinent retrofit schemes after conducting analysis on the air-conditioning system of an industrial enterprise. With comparing the feasibility and the prospective effect of each retrofit scheme, the better one was determined. (C) 2010 Elsevier B.V. All rights reserved.