Based on the analysis of air flow and heat transfer in the dry-cooling tower of Hamon system,a combined iteration method is presented to solve the coupled heat transfer and draft equations derived from theoretical and empirical formulas,with the size of the exchangers and the cooling tower or the systematic parameters being determined.Taking the 686 MW unit as an example,the present calculating results are well agreed with those of the real case,and thus the method presented is practical and feasible for reasonable design of Hamon system.