Abstract: Bleaching is an important process of oil refining.The activated clay was directly sucked in decolorization tank with negative pressure suction.Because of the negative pressure operation，decolorizing effect of oil was not good because of activated clay loss，blend irregularity of clay and oil.Oil decoloring process of premixed before re-entering the bleaching tower for decolorizing agent activated clay and oil was studied.It was applied in cotton seed oil refining process.The activated clay consumption was reduced from 3% to 2%.Refined color was stability controlled within Y35R3.At the same time，oil refining loss was reduced 1%.Economic efficiency of enterprises was improved.