The invention discloses a preparation method of 4, 4 '-dibromo-9, 9'-spirobifluorene, which comprises the following steps: preparing an intermediate product bis (2 '-bromo-[1, 1'-biphenyl]-2-yl) ketone by taking 2, 2 '-dibrominated biphenyl, n-butyllithium and a carbonate compound as raw materials, and carrying out dehydration cyclization reaction on the intermediate product to obtain 4, 4'-dibromo-9, 9 '-spirobifluorene. The method has the advantages of simple synthesis process, easy purification of the product, good product purity, easy purchase of used raw materials, low cost and high yield, and is suitable for industrial production.