The invention relates to a preparation method for pretreating a catalyst by hydrocracking. The method comprises the following steps of: dripping 4 to 8-weight-percent nitric acid and ZrOCl2.8H2O into bayerite, and dripping 1 to 12-weight-percent urotropin solution until liquid is solidified instantly to obtain a zirconium aluminum composite oxide; mixing and kneading with pseudo-boehmite, and extruding for forming to obtain a carrier; and soaking the carrier in a solution containing MoO3 or WO3 and NiO or CoO, drying, and roasting to obtain the catalyst, wherein the catalyst comprises the following components in percentage by weight: 2 to 14 percent of Co or Ni, 8 to 30 percent of Mo or W and the balance of carrier. The catalyst has high activity of hydrogenation reaction, is suitable for the hydrogenation pretreatment process of heavy distillate oil, and provides a high-quality raw material for subsequent processing.