Disclosed are a pretreatment method and system for a fraction oil for the production of alkylbenzene, the method comprising: adding a fraction oil, a weak base solution and an inorganic salt solution into a reactor, and leaving same to stand and layering same after the reaction is complete; adding water and an inorganic salt solution into an oil phase for washing with water; extracting same with a polar solvent having a high boiling point, and then adsorbing same with an adsorbent to separate oxygen-containing compounds in the neutral fraction oil; sending the extraction agent containing the oxygen-containing compounds to an extraction agent recovery unit; and then sending the neutral fraction oil to an alkylation reactor for a reaction.