In this study, glucose, inositol, glycerol, and sorbitol have been chosen as chemical modifiers to enhance laccase stability. The regularity of laccase activity variations was studied at different temperatures. Low concentrations of four polyhydroxyl compounds can improve the thermal stability of laccase at the whole temperature gradient (20~60ºC). The effect of glycerol is best in the all additives, and the relative enzyme activity of laccase increased 1.35 times by glycerol, in the concentration of 0.6 mol/L. The conformation of modified laccase is characterized by UV, fluorescence and circular dichroism. The result shows that the polyhydroxy compounds can change the conformation of laccase by increasing the hydrogen bonds between the laccase molecules and prevent the adverse change due to the increase of temperature in the secondary structure of laccase. Therefore, low concentrations of polyhydroxy compounds could be served as an additive to improve the thermal stability of the laccase. gradient (20~60ºC). The effect of glycerol is best in the all additives, and the relative enzyme activity of laccase increased 1.35 times by glycerol, in the concentration of 0.6 mol/L. The conformation of modified laccase is characterized by UV, fluorescence and circular dichroism. The result shows that the polyhydroxy compounds can change the conformation of laccase by increasing the hydrogen bonds between the laccase molecules and prevent the adverse change due to the increase of temperature in the secondary structure of laccase. Therefore, low concentrations of polyhydroxy compounds could be served as an additive to improve the thermal stability of the laccase.