The invention discloses a preparation method of a hydrodemetallization catalyst. The method includes the following steps that 1, a physical pore-expanding agent I is soaked with an alkali-containing 
metal element solution I and hydrogenation 
active component soaking liquid I, a physical pore-expanding agent II is soaked with an alkali-containing 
metal element solution II and hydrogenation 
active component soaking liquid II, and the physical pore-expanding agent I and the physical pore-expanding agent II are dried and then soaked with an 
ammonium salt solution in a spraying mode for use; 2, the physical pore-expanding agent I and the physical pore-expanding agent II obtained in the step 1 are mixed with dry pseudo-
boehmite gel 
powder, a chemical pore-expanding agent, an 
extrusion aid and a peptizing agent, the mixture is kneaded into plastic, strip 
extrusion is carried out, a formed material is subjected to heat treatment, the treated material is dried and roasted, and a modified 
alumina supporter is obtained; 3, the modified 
alumina supporter is soaked with hydrogenation 
active component soaking liquid III, and the catalyst is obtained through 
drying and 
roasting. The catalyst prepared through the method has a high active 
metal content at macropores and a low active metal content at micropores, the 
acid property at macropores is obviously improved, and the anti-carbon capacity of macropores is improved.