Double-layer roofing system with metal decorative plate and flexible waterproof coil

The invention discloses a double-layer roofing system. The double-layer roofing system sequentially comprises a metal plate device, a waterproof plate, a sound insulation and absorbing heat-insulation plate, purlines and a main support from top to bottom, a plurality of supporting vertical columns are arranged on the main support at intervals, and the purlines and the supporting vertical columns are detachably and fixedly connected; and the supporting vertical columns sequentially penetrate through the sound insulation and absorbing heat-insulation plate and the waterproof plate, the upper ends of the supporting vertical columns are fixedly connected with the metal plate device, the sound insulation and absorbing heat-insulation plate and the purlines are detachably and fixedly connected, and a waterproof sealing structure is formed between the supporting vertical columns and the waterproof plate. Under the situation that the roofing system is provided with a metal decorative plate, the modeling applicability