Study on the reliability of H-beam transfer truss was based on the rebuilding of 1# office building of Chinese Ministry of Commerce. Under construction loads, the force analysis of the H-beam transfer truss was carried out with the software STS2005.12. In the paper, the right of trusses node connection was first chosen, and a plane calculation model of H-beam transfer truss was established based on some reasonable assumptions. Then, the force of H-beam transfer truss under construction loads was analyzed with the calculation model, in determining a reasonable control indexes and calculation parameters. From the results of analysis, we could see that the design and application of H-beam transfer truss in the stage of construction was safe and reliable, in the dismantling concrete post of old structure.