The invention discloses a production method of phosphorus pentoxide through fusing phosphorus ore. Phosphorus ore and silica are mixed pro rata, and delivered to a heating furnace to be heated and molten, after flowing into a reaction furnace, the molten material is charged with carbon, the temperature is controlled to higher than 1200 DEG C, thereby leading the molten material to be deoxidized in the reducing zone of the reaction furnace, generating P4 vapour and CO gaseous mixture and absorbing heat, the gas directly oxidizes with the added oxygen in the oxidation zone of the reaction furnace, thereby generating P2O5 gas and CO2 gas and releasing heat, the heat is provided for heating the molten materiel and the heat picking of the reduction reaction, thereby controlling the oxygenationmode in the oxidation zone and maintaining the reducing atmosphere on the molten liquid interface of the reaction furnace, and leading the reduction reaction and the oxidation reaction to be respectively successfully performed, and the P2O5 gas generated is prepared into the phosphorus pentoxide product through cooling and cleansing. The invention has the advantages that the flow is simplified, the cost is reduced, the finished quality is improved, the percent reduction of the phosphor reaches to 98 percent, the energy and resource are saved, the three wastes are basically eliminated, therefore, the invention provides an epoch-making revolution for the phosphor chemical engineering industry.