Since the natural laccase is inclined to be inactivated at industrial application conditions, it is especially important and urgent to improve the stability of laccase. Taking laccase secreted by Pleurotus ostreatus as the research object, the laccase is chemically modified with dextran (Dex) and succinic anhydride (SA). The pH stability, thermal stability as well as degradation efficiency toward indole of natural laccase and modified laccase are compared. The enzyme-catalyzed reaction reveals the Michaelis–Menten constant K_m value of modified laccase rises, while the pH stability and thermal stability of modified laccase are superior to those of natural laccase. Moreover, the degradation efficiency toward indole for dextran modified laccase (Dex-Lac) and succinic anhydride modified laccase (SA-Lac) are 37.2% and 35.3% at 50ºC after 3h, respectively, achieving nearly 2 times higher than natural laccase.