tEfficient utilization of hemicellulose entails high catalytic capacity containing xylanases. In this study,proline rich sequence was fused together with a C-terminal of xylanase gene from Geobacillus ther-modenitrificans C5 and designated as GthC5ProXyl. Both GthC5Xyl and GthC5ProXyl were expressed inEscherichia coli BL21 host in order to determine effect of this modification. The C-terminal oligopep-tide had noteworthy effects and instantaneously extended the optimal temperature and pH ranges andprogressed the specific activity of GthC5Xyl. Compared with GthC5Xyl, GthC5ProXyl revealed improvedspecific activity, a higher temperature (70◦C versus 60◦C) and pH (8 versus 6) optimum, with broadranges of temperature and pH (60–80◦C and 6.0–9.0 versus 40–60◦C and 5.0–8.0, respectively). Themodified enzyme retained more than 80% activity after incubating in xylan for 3 h at 80◦C as comparedto wild −type with only 45% residual activity. Our study demonstrated that proper introduction of prolineresidues on C-terminal surface of xylanase family might be very effective in improvement of enzyme ther-mostability. Moreover, this study reveals an engineering strategy to improve the catalytic performanceof enzymes