The invention discloses a method for producing diesel oil by utilizing a Fischer-Tropsch synthesis product. The method comprises the following steps: 1, separating the Fischer-Tropsch synthesis product to obtain LPG, naphtha, straight-run diesel oil and heavy oil; 2, carrying out hydroisomerization cracking of the heavy oil, carrying out an alkylation reaction of LPG and naphtha fractions in the synthetic oil product obtained after the hydroisomerization cracking and LPG and naphtha obtained in step 1, and hydrofining the diesel oil fraction in the synthetic oil product obtained after the hydroisomerization cracking and the straight-run diesel oil obtained in the step 1; and 3, mixing the diesel oil fraction in the obtained alkylation reaction product with hydrofinished diesel oil obtained after the hydrofinishing reaction to realize the production of diesel through utilizing the Fischer-Tropsch synthesis product. The method allows the alkylation reaction of the straight-run diesel oil fractionated from the Fischer-Tropsch synthesis product to be carried out, so the load of the hydrofinishing unit is obviously reduced. Only the diesel oil fraction is hydrofinished, so the raw material distillation range is narrow, thereby the method enables the hydrofinishing condition to be mild and the technology to be simplified.