Directed evolution of β-xylosidase XylBH43 using a single round of gene shuffling identified three mutations， R45K， M69P， and L186Y， that affect thermal stability parameter K(t)⁰·⁵ by -1.8 ± 0.1， 1.7 ± 0.3， and 3.2 ± 0.4 °C， respectively. In addition， a cluster of four mutations near hairpin loop-D83 improved K(t)⁰·⁵ by ~3 °C; none of the individual amino acid changes measurably affect K(t)⁰·⁵. Saturation mutagenesis of L186 identified the variant L186K as having the most improved K(t)⁰·⁵ value， by 8.1 ± 0.3 °C. The L186Y mutation was found to be additive， resulting in K(t)⁰·⁵ increasing by up to 8.8 ± 0.3 °C when several beneficial mutations were combined. While k cat of xylobiose and 4-nitrophenyl-β-D-xylopyranoside were found to be depressed from 8 to 83 % in the thermally improved mutants， K(m)， K(ss) (substrate inhibition)， and K(i) (product inhibition) values generally increased， resulting in lessened substrate and xylose inhibition.