The invention provides a method for controlling an alkali liquor in a cold-rolling strip steel cleaning section. The alkali liquor is arranged in an alkali liquor circulating tank. The method comprises the following steps of determining residues on the surface of strip steel through a weight method, and obtaining the contents alpha (mg/m<2>) of residual oil and residual iron per unit area of the surfaces of the strip steels in different steel grades; obtaining operating speeds V (m/min) of the strip steels; obtaining widths W (mm) of the strip steels; obtaining pollutants L (L is equal to V*W*alpha*60*10<-9>) carried into the cleaning section by the strip steels with different specifications at different speeds per unit time; obtaining a liquor oil content standard value beta of the alkaliliquor circulating tank through an oil-water separation device; and obtaining a theoretical alkali liquor discharge amount Q (Q is equal to 10*L/beta) of the cleaning section per unit time. Accordingto the method for controlling the alkali liquor in the cold-rolling strip steel cleaning section provided by the invention, a guiding significance is provided for an actual discharge amount and a supplementary amount of the alkali liquor and an addition amount of a defoaming agent, the positive cycle of the alkali liquor in the alkali liquor circulating tank is realized, meanwhile, a cleaning effect is improved, and the practical application proves that the method solves the problem that a solution of the cleaning section is bubbled since the liquor is not discharged timely or the defoaming agent is added unreasonably.