The invention discloses an auxiliary XYJ for cotton fiber hydrogen peroxide positioning catalytic pretreatment, a preparation method of the auxiliary and an application of the auxiliary. The pretreatment auxiliary XYJ is prepared from, in weight percent, 1%-2% of ethyl acetate, 20%-30% of dimethyl sulfoxide, 10%-30% of glycerol, 5%-10% of isopropanol and 28%-64% of purified water. By the aid of the auxiliary for cotton textile pretreatment, cotton fibers or the cotton textiles to be treated are placed into a pretreatment device, water is added, and dye bath circulation is kept. A hydrogen peroxide positioning catalytic compound auxiliary XAT and the pretreatment auxiliary XYJ disclosed by the 'hydrogen peroxide positioning catalytic compound auxiliary and an application thereof to cotton pretreatment' are used for pretreating the cotton fibers or the cotton textiles in a pretreatment device, the water absorption capability (capillary effect) of the treated cotton fibers or the cotton textiles can be remarkably improved, and quality indexes of products are further improved.