The test of four large scale specimens of floor system with P.C. long-span beams is introduced.The restraining torsional moment of spandrel beams caused by P.C. beams with or without slab is focused on,along with change of the load-torque relationship affected by the beams' bending rigidity and the spandrel beams' torsional rigidity under different load level. The result presents important reference to the revision of national design standard and structural design.