The invention discloses a method for treating liquid waste of silicon steel passivation solution, which belongs to the technical field of the 'three wastes' (waste gas, waste water and industrial residue) treatment in the iron and steel industry. The method comprises the following steps of: firstly, collecting, mixing and homogenizing the liquid waste of the silicon steel passivation solution by using an acid-base adjusting tank, wherein the pH value is adjusted to be 3 to 4; secondly, injecting the liquid waste into a reaction tank by using a sewage pump; thirdly, adding FeSO4.7H2O and 30 percent hydrogen peroxide (H2O2) into the reaction tank so that the molar ratio of iron ion to H2O2 to chromium ion is 5.2:10.4:1, wherein the temperature is maintained to be between 15 and 35 DEG C andthe residence time is 60 minutes; fourthly, after the reaction treatment, allowing the mixed solution to automatically flow into a neutralizing tank, adding alkali to adjust the pH value to be 7 to 8, and allowing the mixed solution to automatically flow into a sedimentation tank; and finally, discharging supernatant in the sedimentation tank, allowing settled sludge to enter a chromium residue concentration tank to concentrate and then automatically flow back to the acid-base adjusting tank, allowing the remained chromium residues to enter a centrifugal machine to dehydrate, recovering the dehydrated residue cakes and allowing residue liquid to flow back to the acid-base adjusting tank. By the method, the chromium and chemical oxygen demand (COD) can be removed synchronously, the chromium in the liquid waste can be recovered, and the reclamation of the liquid waste of the silicon steel passivation solution can be realized.