The invention discloses a method for improving particle fluidization quality and separation density stability and a matched device. In a gas-solid fluidized bed dry separation system, coarse particlesand fine particles are selected as separation media, the coarse particles and the fine particles are sufficiently mixed, a separation bed layer having a certain density is formed under the action ofairflow, the size of the coarse particles is not larger than 500 microns, the size of the fine particles is not larger than 45 microns, and the aerodynamic diameter ratio of the coarse particles to the fine particles is not less than 5. The matched device comprises a gas-solid fluidized bed body, a wind supply device, a material level height testing device, a scraper conveyor device, a density measuring device and a dust removing device. According to the method and the matched device, the fine particles are introduced, so that the fluidization quality of the medium particles is improved, the bubble size is reduced, the separation density stability is improved, the mineral separation accuracy is improved, and efficient separation of coal is achieved. The device does not need water, is simple in operation and maintenance, free of pollution and low in investment and operation cost, and has significant economic and social benefits.