A preparation method of highly pure 2-bromofluorene belongs to the technical field of synthesis of organic matters. The 2-bromofluorene is prepared from 2-aminofluorene and hydrobromic acid. The preparation method comprises the following steps: placing the hydrobromic acid and the 2-aminofluorene in a reactor, stirring the above raw materials, heating the raw materials, carrying out a refluxing reaction for 2-3 h, cooling the obtained reaction product to 40-60 DEG C, adding a cuprous compound, uniformly stirring the cuprous compound and the cooled reaction product, dropwise adding a nitrous acid compound, carrying out a heat insulation reaction for 1-2 h after the dropwise addition is finished, adding toluene to dissolve the obtained heat insulation reaection product, and carrying out filtration desalting, liquid separation, water washing and organic layer concentration to obtain the 2-bromofluorene. The preparation method has the advantages of simplicity, mild and stable reaction product, realization of direct obtaining of the 2-bromofluorene through a one-pot technology, and high yield and high purity of the obtained 2-bromofluorene.