The invention relates to an adsorbent for adsorbing and separating polycyclic aromatic hydrocarbons and a preparation method thereof; the adsorbent is composed of a Y molecular sieve carrier and metal ions exchanged on the Y molecular sieve carrier in a particular order, wherein the metal ion content is 0.1 wt%-30 wt%. The preparation method of the adsorbent comprises that kaolin is firstly subjected to high temperature pretreatment activation, an appropriate amount of an active silicon source is added during synthesis, then a sol is subjected to dynamic aging crystallization, next the metal ions are subjected to ion exchange through two or multiple times of contact in a certain order, and thus the adsorbent is obtained. The adsorbent has a stronger adsorption capacity on the polycyclic aromatic hydrocarbons and can effectively adsorb and separate the polycyclic aromatic hydrocarbons in diesel oil, and the removal rate can reach 80%.