Thermophilic and alkalophilic xylanases have great potential in the pulp bleaching industry. In order to improve the thermal stability of an alkaline family 11 xylanase Xyn11A-LC, aromatic residues were introduced into the N-terminus of the enzyme by rational design. The mutant increased the optimum temperature by 5 ℃. The wild type had a half-time of 22 min at 65 ℃ and pH 8.0 (Tris-HCl buffer). Under the same condition, the mutant had the half-time of 106 min. CD spectroscopy revealed that the melting temperature (Tm) values of the wild type and mutant were 55.3 ℃ and 67.9 ℃, respectively. These results showed that the introduction of aromatic residues could enhance the thermal stability of Xyn11A-LC.