Abstract: Prestressed space grid structure is a new type of space structures combining the modern prestressing technology with long-span space structures. A new method for multi-step pretensioning analysis of prestressed space grid structures is presented in this paper. Based on the method of structural mechanics and the principle of linear superposition, the standard equations of unknown prestressing forces of prestressed members during each prestensioning step can be established and solved. The governing internal forces of prestressed members, the internal forces of unprestressed members as well as the nodal displacements can then be obtained easily. Prestensioning members according to the obtained governing forces, the designed prestressing forces of prestressed members will be reached automatically. An orthogonal square space structure pretensioned by five-step is analyzed. The numerical results show that the proposed method is correct, reliable and effective and can be applied into linear analysis of prestressed space grid structures and other pretension systems.