The invention relates to a preparation method of a hydrofining catalyst, in particular to a preparation method of a platinum-palladium double-metal hydrodearomatization catalyst. The method comprisessteps as follows: S1, an aluminum-silicon mixed metal oxide composite carrier precursor is prepared firstly; S2, a palladium precursor salt solution, a platinum precursor salt solution and a platinum-palladium mixed precursor salt solution which have different concentrations are prepared; S3, one precursor salt solution is taken to impregnate the carrier precursor; drying and calcination under thevacuum condition are performed; S4, an obtained sample is impregnated in a metal salt solution which is different from the precursor salt solution used in S3; a prepared sample is subjected to certain drying, calcination and reduction treatment, and the novel platinum-palladium double-metal catalyst is obtained. The prepared catalyst can reduce the use amount of platinum to a certain extent, still keeps better aromatic hydrogenation activity and is particularly applicable to the hydrofining process of clean diesel, high-quality lubricating oil base oil and white oil which are prepared from raw oil with high aromatic hydrocarbon content.