The invention discloses a sendzimir 20 rolling mill edge plate shape controlling method and device. The method comprises the following steps that (1) strip steel plate shape actual values in all control periods are obtained; (2) operation side edge plate shape deviations and driving side edge plate shape deviations are obtained by subtracting target plate shape values from the plate shape actual values; (3) symmetrical side plate shape deviations are calculated according to strip steel two-side edge plate shape deviations; (4) side plate shape control gain coefficients are calculated; (5) symmetrical side plate shape deviations multiply by the side plate shape control gain coefficients to obtain a middle roller symmetrical moving adjustment amount; and (6) the adjustment amount is output to a mill. By means of the sendzimir 20 rolling mill edge plate shape controlling method and device, the stability in the rolling process is guaranteed, the side plate shape control effect is guaranteed, and the problem of moving of non-symmetrical middle rollers is solved.