The invention provides a preparation method of an impregnation solution for a reforming pre-hydrogenation catalyst. The preparation method is characterized in that the solution comprises Mo, Ni, Co, W, Mg, P and an additive; 100 ml of the solution contains 10 g -16 g of MoO3, 5 g-9 g of NiO, 3 g-5 g of CoO3, 20 g-28 g of WO3, 0.5 g- 2 g of MgO, and 5 g-15 g of the additive; and the molar ratio of P to MoO3 ranges from 0.3 to 0.5. The preparation process comprises the steps of heating a phosphoric acid water solution to 70 DEG C-80DEG C; adding molybdenum trioxide, heating the solution to boiling, and stirring the solution until dissolution; cooling the solution to 70 DEG C-80DEG C; adding basic nickel carbonate slowly, heating the solution to boiling, and stirring the solution for dissolution; concentrating the solution to a required volume; cooling a concentrated solution to the room temperature; adding cobalt nitrate and stirring the solution for dissolution; adding ammonium metatungstate and stirring the solution for dissolution; adding a magnesium compound and stirring the solution for dissolution; adding the additive and stirring the solution for dissolution; and determining the volume to obtain the impregnation solution.