The invention provides a method for preparing rod-shaped spinel manganese ferrite through a seed-hydrothermal method, relating to a method of using orderly rod-shaped Mn2O3 to prepare rod-shaped spinel manganese ferrite. The method comprises the following steps: 1 mol/L ferric chloride solution, 2 mol/L manganese chloride solution and 2.5 mol/L sodium hydroxide solution are prepared; the orderly rod-shaped Mn2O3 is used as a seed; the ferric chloride solution and the manganese chloride solution are weighed according to the MnFe2O4 stoichiometric ratio (2:1) and are orderly put into an inner liner of a hydrothermal reaction kettle, and react under the stirring of a magnetic stirrer; the sodium hydroxide solution is put into chlorate mixture drop by drop, and pH value is regulated; reactionlasts for 12 to 15 hours; after the reaction is over, the chlorate mixture is cooled to room temperature, and precipitate is washed; and the obtained sample is dried. Compared with the prior method, the method of the invention prepares a complex special-form compound from a simple special-form oxide, improves performance, and is simple in process, easy to control, good in form and crystallinity degree, low in synthesis cost, environment-friendly, energy-saving, easy to operate and probable to be applied to the preparation of other special-form composite oxides.