The invention discloses a rail steel refining method. The rail steel refining method includes the steps that in the converter steel tapping process, active lime is adopted for conducting slag washing, and then calcium carbide is adopted for modifying ladle top slag; a modified steel ladle is sent to an LF for conducting slag adjusting, the active lime and the calcium carbide are adopted for refining, adding is carried our two times in the adding process, and the argon flow meets the conditions that the argon flow at the earlier stage ranges from 100 Nl/min to 200 Nl/min, the argon flow at the medium stage ranges from 100 Nl/min to 200 Nl/min, and the argon flow at the later stage ranges from 100 Nl/min to 150 Nl/min. The sulphur content in molten steel obtained after LF processing is smaller than or equal to 0.006%, silica sand is added at the later LF processing stage for reducing the alkalinity of the steel ladle slag, then refining is continuously carried out for an appropriate time, and the steel ladle slag is sent for conducting vacuum processing. The rail steel refining method is suitable for producing high-quality rail steel, and the sulphur content in the steel is smaller than or equal to 0.006%.