The invention discloses a biochemical pretreating agent for industrial wastewater, and belongs to the field of industrial wastewater treatment. The biochemical pretreating agent is prepared from 0.5-5% of sodium gluconate, 0.5-2% of citric acid, 1-6% of proteolytic enzymes, 0-1% of dipotassium phosphate, 0-4.5% of ammonium chloride and the balance distilled water. The biochemical pretreating agent has the advantages that toxic effects of toxic substances in the industrial wastewater on biochemical systems can be effectively reduced, and accordingly the refractory industrial wastewater can be effectively treated.