The invention discloses an energy-saving mineral wool preparation system with a thermal-state slag and aims to provide the energy-saving mineral wool preparation system which not only can fully utilize residual heat resources in blast furnace thermal-state slag and is energy-saving and environmental-protective but also can enable a melt in a slag furnace to be melted uniformly, a vitrification degree to be high and a fiber-forming ratio and quality of mineral wool to be improved. The device includes a slag furnace and at least two centrifugal machines. The slag furnace successively includes a feeding tank, a homogenizing tank, a melting tank, a clarifying tank and at least two material paths. A slag flow inlet and a main modulating material feeding port are arranged on an upper part of the feeding tank. The bottom of the feeding tank is connected to the bottom of the homogenizing tank through a first liquid flowing path. The bottom of the homogenizing tank is communicated with the bottom of the melting tank through a second liquid flowing path. The clarifying tank is communicated with the melting tank through a third liquid flowing path. One end of each material path is communicated with the clarifying tank and the other end of each material path is closed. In addition, material outlet ports are arranged at the bottoms of the material paths.