The static weight loss method, potentiodynamic polarization and observing microscopic appearance were used to study the synergistic effect of fatty alcohol ethoxylates (peregal O-20) and complexd inhibitors on corrosion inhibition of Q235 steel in the chlorine dioxide media of 100 mg/ L. The results show that peregal O-20 has a corrosion inhibiting effect for Q235 steel,but the amount of corrosion inhibitor is large when used alone; Composite peregal O-20 with sodium nitrate or sodium molybdate or sodium benzoate can produce synergistic inhibition effect on Q235 steel,when composite with sodium benzoate can produce the most obvious synergistic inhibition effect; When the concentration ratio of sodium benzoate and peregal O-20 is 6 : 4 and the total dosage of 300 mg/ L,the maximum inhibition efficiency can achieve 92. 55% .