The use of SN steel in the building structure improved the reliability of the building. As a preceding study, the material properties of SPAR295 square pipes manufactured using SN400B plates were evaluated. The yield and ultimate strengths at the edges of SPAR295 square pipes did not satisfy the design codes based on the values at the sides. The bending tests of cold rolled steel square pipes for aseismatic building structures are performed. The main results show that: 1) the ultimate bending strength is much great, and the energy dissipation capacity is very well, which can make to consume great energy in earthquake. This SPAR295 can meet the need of seismic design very well. 2) The specimens are showed long yield platform after yielding, great cumulative energy-dissipating capacity and well ductility. 3) The fracture of specimens are caused by the local buckling and fracture of welding vicinity.