The invention provides a method for preparing a mask base cloth. The method for preparing the mask base cloth comprises the steps that the preparation of a modified fiber and the preparation of a blended fiber base cloth are carried out, specifically, according to the preparation of the modified fiber, an unsaturated amino acid modified viscose fiber is adopted, specifically, 0.01-0.3 part, by weight, of an emulsifier and a 0.015-0.5 part, by weight, of a pH regulator are added in 100 parts, by weight, of water, then 10-30 parts, by weight, of the viscose fiber is added, under nitrogen atmosphere, 0.01-0.1 part, by weight, of an initiator is added, then unsaturated amino acid is added, 0.01-1 part, by weight, of a chain transfer agent is added after the reaction is started, and amino acidmodified viscose fiber is obtained by washing and drying after the reaction. The mask base cloth solves the problem that the improvement of mechanical properties reduces the bonding degree and liquidretention rate of the base cloth, so that the base cloth has excellent mechanical properties, meanwhile, the flexural rigidity of the base cloth is reduced, and the flexural rigidity is as low as 0.0132gf.cm<2> / cm, the flexibility is good, the bonding degree of the base cloth to the skin is improved, and the liquid retention rate of the base cloth is improved and can reach 2702%.