Abstract: This form of buildings have been constructed about 60000m² since 1974 in the city of Nantong,because the ceiling is smooth,without projecting structural elements and its construction cost is cheaper,so it is greatly welcomed by factories.Structural analysis proved that this system is a static geometrical invariable system,stable structure.The carried out tests show that the performances of inverted double T slab and air conditioning duct beam are satisfactory.