In the present study, a program for predicting thermal performance of an air cooled condenser is illustrated. Heat transfer equations of single phase and two phase flow are formulated into the form that is convenient to incorporate the local analysis method. The resulting equations are solved by temperature and mass correction methods. Empirical equations for both side fluids are incorporated in the caculation procedures. In order to compare the calculation results, superheat temperature of steam are varied. The tube length of superheated zone, wall temperature, temperature profile along the tube and steam qualities are predicted.