The invention discloses a method for preparing trimanganese tetroxide by using rhodochrosite, comprising the following steps of: lixiviating the rhodochrosite by using a sulfuric acid solution to prepare a manganese sulfate solution; then purifying the manganese sulfate solution; then adding ammonia water to the purified manganese sulfate solution so that divalent manganese ions contained in the manganese sulfate solution generate manganese hydroxide precipitates; desulphurizing and washing the manganese hydroxide precipitates, and then oxidizing the washed manganese hydroxide precipitates byutilizing air or oxygen; and finally washing and drying to obtain a trimanganese tetroxide finished product. The preparation method not only has a simple process and low cost, but also has high purity and recovery rate and large specific surface area of a prepared product.