Method for improving diesel oil yield of process for producing diesel oil from Fischer-Tropsch synthesis oil product

The invention provides a method for improving the diesel oil yield of a process for producing diesel oil from Fischer-Tropsch synthesis oil products and a device for implementing the method. The method comprises the following steps: carrying out ammonia water neutralization on Fischer-Tropsch synthesis light oil and Fischer-Tropsch synthesis heavy oil, then mixing with Fischer-Tropsch synthesis heavy wax, carrying out hydrofining reaction, and carrying out gas-liquid separation and fractionation on a hydrofining reaction product to obtain refined naphtha, refined diesel oil, refined heavy oil, refined tail oil and the like; carrying out a cracking reaction on the refined tail oil, and carrying out a pour point depressing reaction on the refined heavy oil; carrying out cracking separation and fractionation on the obtained pour point depressing reaction product and the cracking reaction product to obtain LPG, cracked naphtha, cracked diesel oil, cracked heavy oil, cracked tail oil and the like; carrying out a c