The invention belongs to the field of alkali liquor filtering in preparation of alkali from viscose production, and particularly relates to a method for alkali liquor filtering. The method comprises the steps that 1, impregnated and squeezed alkali liquor is subjected to preprocessing through a filter bag type filter, and fiber inside the alkali liquor is filtered away; 2, the alkali liquor obtained after being treated through the filter bag type filter passes through a drum type automatic fiber and then is subjected to one secondary filtering; 3, waste liquor obtained after backwashing of the filter bag type filter and the drum type automatic filter is subjected to filter pressing through a filter press; 4, the alkali liquor obtained after being filtered through micropores sequentially pass through safety filtering and nano-filtration membrane filtering, and finally the alkali liquor filtered by the nano-filtration membrane is recycled into the step of impregnation. in the first and second steps, the length of intercepted fiber is 0.3-1.2 millimeters, the pore diameter of a filter net of the drum type automatic filter adopted in the second step is 10 micrometers, a filter layer is formed on the inner side of the filter net after filtering is performed for a period of time so as to achieve the intercepting effect, and therefore 99% fiber inside the alkali liquor can be filtered away in the second step.