The invention provides a method for preparing rare-earth fluoride/rare-earth oxyfluoride composite nano-fiber, belonging to the technical field of inorganic fiber preparation. The prior art comprises the nano-fiber, an electrostatic spinning method and the rare-earth fluoride/rare-earth oxyfluoride. The technical problem solved by the invention is to prepare the rare-earth fluoride/rare-earth oxyfluoride nano-fiber by the electrostatic spinning method. The method comprises the following steps: firstly, preparing spinning solution; dissolving rare-earth salts into the solution, the rare-earth salts are salts with one or more than one rare-earth element; stirring the mixed solution to produce rare-earth salts solution; adding a high molecular template agent into the rare-earth salts solution with stirring to produce solution of the rare-earth salts and the high molecular template agent; stirring and adding ammonium fluoride into the solution of the rare-earth salts and the high molecular template agent with stirring to produce a rare-earth fluoride/high molecular template agent mixed the spinning solution, with the percentage by weight being 2 to 5 percent of rare-earth fluoride, 15to 20 percent of the high molecular agent, and 75 to 83 percent of solution; secondly, the method prepares a precursor fiber for the rare-earth fluoride/high molecular template agent by the electrostatic spinning method; and thirdly, rare-earth fluoride/rare-earth oxyfluoride composite nano-fiber is prepared through heating treatment.