The invention discloses a heat-storage heat-preservation formwork for a precast box beam. The heat-storage heat-preservation formwork for the precast box beam comprises multiple groups of heat-storageheat-preservation structures; wherein lead wire assemblies are arranged among the multiple groups of heat-storage heat-preservation structures; the heat-storage heat-preservation structures compriseformwork mechanisms and supporting mechanisms arranged at the lower ends of the formwork mechanisms; multiple groups of heating mechanisms are arranged between the formwork mechanisms and the supporting mechanisms, are in parallel, and are longitudinally arranged between the formwork mechanisms and the supporting mechanisms; the heating mechanisms comprise electric heating tapes and rock wool boards; and the electric heating tapes are connected to the upper ends of the rock wool boards. The heat-storage heat-preservation formwork is simple in structure, and the precast beam can be well heat-preserved and cured. The invention further discloses an application method of the heat-preservation formwork. By adopting the heat-storage heat-preservation formwork for the precast box beam, the heat-storage heat-preservation formwork for the precast box beam can be well installed and used according to the application method of the heat-preservation formwork and is prevented from being damaged excessively.