The invention discloses a process for smelting ultra clean steel by a single-nozzle refining furnace, belonging to the technical field of ferrous metallurgy. The process comprises the followings steps of: blowing in argon gas from the bottom of steel ladle with the blowing gas flow quantity of 1-10 NL/min per ton of steel, and inserting a suction nozzle into the steel ladle; carrying out a vacuum natural decarburization technology when the initial carbon content in liquid steel is smaller than 0.035%, and carrying out a vacuum forced decarburization technology when the initial carbon content in the liquid steel is greater than 0.035%, wherein the time for decarburization is 12-22 min; after decarburization, maintaining the pressure of a vacuum chamber to be les than 100-200 Pa, adding 1-6 kg of deoxidizer per ton of steel, and adding 0.5-8 kg of desulfurizer per ton of steel in 1-2 min after the deoxidizer is added, wherein the flow quantity of argon gas is 1-10 NL/min per ton of steel, and the time for desulfurization is 5-15 min; and deoxidizing and removing impurities after desulfurization. The process can simultaneously reduce the content of impurity elements comprising carbon, sulfur, nitrogen, hydrogen and oxygen and impurities in the liquid steel to an extremely low level within limited refining time, and the refining efficiency is obviously superior to that of an RH refining furnace.