Lingzhao Xuan in the Forbidden City is one of the oldest steel-masonry composite structures. The building is seriously damaged now. In order to better conserve and restore the building, scientific researches on the damage to and the structural performance of this building are of great importance. Our research was carried out as follows:first, damage to the building was assessed by on-site observation of visible damage. Then the structural performance of the building was studied by accurate survey of damage, nondestructive test and finite element model (FEM) analysis to assess potential damage. Finally, based on these investigations, a conservation strategy for this building was proposed based on the results of these damage investigations and theoretical analysis.