Abstract: The space grid structure is increasingly utilized in modern architecture due to its unique architectural design. With the growing complexity of space grid structure and the main structure below it, the structural installation technology is continuously improving and evolving. For a single-layer three-way grid structure with a complex lower supporting structure, the conventional method of installing insitu block installation using temporary supporting frameworks or erecting full-height scaffolding for high-altitude bulk installation poses challenges such as excessive measures, high costs, and long dismantling times. New construction methods like hydraulic overall synchronous lifting, jacking, and skidding not only face issues of cost and efficiency but also involve higher construction difficulty. Addressing the mentioned issues, the key technology of unsupported construction is studied, taking the saddle-shaped single-layer three-way grid dome structure in the sunken plaza of Shenzhen’ s “ Internet+” Future Science and Technology City Lot DY01-04 as an example, aiming to achieve fewer temporary support measures and increased construction efficiency. Unsupported construction involves using a specific blocking method to fully utilize the previous lifting unit as the support structure for the next unit and complete the installation in a staggered manner without temporary support. The key to the construction is that each block divided by the specific blocking method can form a stable structural system with the previous installation structure post-lifting completion, preventing excessive displacement and stress compared to the one-time design pattern. Through simulation analysis of the entire construction process and onsite monitoring data, and considering safety, convenience, and cost-effectiveness of the construction process, a comparative study of three unsupported construction methods-spiral, unidirectional staggered, and symmetric staggered is conducted. The study indicates that unsupported construction for single-layer three-way grid structures is safe, reliable, and close to the design state in terms of structural stress and deformation after completion, with minimal overall structural stress and no stability issues in the construction process of the ring girder, showing sufficient safety margin. Unsupported spiral construction has a shorter segment length, better structural stress and deformation of the total structure compared to unsupported interlocking construction, while unsupported symmetric staggered construction effectively reduces the additional stress and deformation caused by the “ see-saw ” effect in the construction process, making it superior to unsupported unidirectional staggered construction. By placing deformation and stress monitoring points where simulated structural displacements and stresses are significant, monitoring the structural deformation and stress during the construction process reveals that the actual structural deformation and stress align closely with MIDAS simulation and analysis results in trend and numerical value, demonstrating the rationality of the unsupported spiral construction scheme.