The invention concerns a process for the pre-treatment of an unrefined vegetable or animal oil, consisting of passing said oil through a reactor comprising at least one fixed bed of at least one adsorbent comprising a porous refractory oxide which is free of catalytic metals, at a temperature in the range 130° C. to 320° C., at a pressure in the range 0.1 to 7 MPa and with a residence time for said oil on said fixed bed in the range 0.1 to 1 hour. The invention concerns a process for pre-treatment of a semi-refined vegetable or animal oil, integrated upstream of a hydrotreatment step for the production of green gas oil.