The invention discloses a preparation method, a use method and applications of magnetic carbon nano-tubes. The preparation method comprises: preparing a certain amount of an aqueous solution containing manganese chloride and ferric chloride in a conical flask; adding an appropriate amount of carbon nano-tubes, and stirring uniformly; under a certain stirring speed, carrying out water bath heatingto a temperature of 50-70 DEG C, adding a sodium hydroxide solution, and adjusting the pH value to 9-11; carrying out thermal insulation for 4 h in a water bath pot; cooling, repeatedly rinsing with deionized water, carrying out magnetic separation from the aqueous solution, and drying so as to be spare; metering a certain volume of solutions respectively containing humic acid, methylene blue, methyl orange, phosphate radical, tetracycline and copper ions, and determining the concentrations of the six solutions; respectively weighing a certain amount of the magnetic carbon nano-tubes, adding to the six solutions respectively containing humic acid, methylene blue, methyl orange, phosphate radical, tetracycline and copper ions, adsorbing for 24 h in a 25 DEG C 140 rpm shaking table, respectively sampling, filtering the samples with a filtration membrane, and respectively detecting the concentrations. According to the present invention, the product is suitable for the removal of various pollutants in a water body.