Addition of additives has been confirmed to increase cellulase performance in the hydrolysis of lignocellulosic materials. In the hydrolysis of xylan-containing lignocellulosic biomass, xylanase can synergistically enhance the performance of cellulase. However, the role of additives in xylan hydrolysis by xylanase is not yet clear. In this work, with the presence of additives (bovine serum albumin, poly(ethylene glycol), and Tween), the hydrolysis of isolated xylan and the xylan in corn stover increased to different extents. Additives increased free xylanase in supernatants in the hydrolysis with xylanase, indicating the reduction of the adsorption of xylanase on corn stover and insoluble xylan. Enhanced hydrolysis of Avicel and corn stover by additives suggested that besides the prevention of unproductive binding of xylanase to lignin by additives, reducing the adsorption of xylanase on substrates was also contributed to enzymatic hydrolysis. The increment of xylanase activity by additives suggests that the additives were activators of xylanase. The results of this work indicate that the supplementation of additives could improve xylanase performance, synergistically enhanced the cellulose hydrolysis, and beneficial for the recycling of xylanase.