The invention relates to the technical field of heat conduction of electric devices and especially relates to a circuit floating mounting structure. The circuit floating mounting structure includes a support framework. At least one group of reversely threaded mechanisms capable of moving up and down is mounted on the support framework. Each group of the reversely threaded mechanisms includes two reversely threaded mechanisms mounted in the same direction. At least one group of circuit board and heat dissipation board spaced from each other is mounted between the two reversely threaded mechanisms mounted in the same direction. The heat dissipation board presses against the cabin wall of an electric cabin accommodating the heat dissipation board after being driven by the reversely threaded mechanisms to move and reaching a predetermined height. The relative positions of the circuit board and the heat dissipation board can be adjusted quickly and semi-automatically, so that contact between a heat dissipater and the inner wall of the electric cabin is promoted and the environmental adaptability of the electric device is improved. At the same time, the gap between the circuit board and the electric cabin can be enlarged in the initial stage of a mounting process, so that the mounting difficulty is reduced, the gap between the circuit board and the electric cabin can be reduced and heat dissipation is facilitated.