The invention belongs to the technical field of light chemical engineering, and particularly relates to application of a pyridine double-acid modified cellulose adsorbent. By the adsorbent, dyestuff in an aqueous solution can be removed selectively, meanwhile, the dyestuff can further be recycled, the application has certain environmental protection significance and economic value, the cost is low, the adsorption capacity is large, adsorbability is stable, the adsorbed dyestuff can be secondarily utilized, and the application of the pyridine double-acid modified cellulose adsorbent has the advantages of great energy conservation and emission reduction, and environmental protection.