With the developments of the design theories and the researches, the quantity and the technology of space truss systems in our country have reached the international leading level. In the meantime, the construction methods need to achieve even higher standard. In the article, the rhombic space truss roof of the north station building of Suzhou is selected as the research object. Each step of the sliding and unloading construction is simulated by FEM. The stability and rigidity of the truss are checked in detail. It gives an representative exsample for complicated construction design of large-span space trusses.