The invention provides a double-layered roofing system for improving heat insulation performance, which comprises a plurality of purlins, multiple roofing bottom plates installed on the purlins and connected in order and multiple roofing ceilings located at the upper parts of the roofing bottom plates and connected in order; a first heat insulation material is filled between the roofing ceilings and the roofing bottom plates, and a second heat insulation material is filled between adjacent two purlins. According to the double-layered roofing system for improving heat insulation performance, the heat insulation materials are filled between the roofing ceilings and the roofing bottom plates and between adjacent purlins; through the two-layered heat insulation materials, the heat insulation effect of the roofing system can be ensured.