Through some reasonable assumptions

a two-fork tree model for tree-branch type steam pipe network with a single heat source has been established.By using the algorithm of single cycle and twice interation

the problem related to thermodynamic calculation of pressure and temperature for a single pipe has been solved.Based on iterative algorithm of thermodynamic calculation for a single pipe

and combining with the structural features of a two-fork tree

a software for thermodynamic calculation of tree-branch type pipe network has been worked out.Adopting concrete example from design calculation

and through checking caclulation of varying operating conditions

the correctness of software algorithm and reliability of steam pipe netwok designed by using the said software have been verified.