The effects of adding 0.005,0.01,0.015 mg/mL oligosaccharin on activity of laccase in the liquid medium containing sawdust of three stains Pleurotus sp.were studied.The results showed that three concentration of oligosaccharin all had marked effects to the activity of laccase.The most obvious effect was to ’Jiwei 961’ P.ostreatus,in which the activity of laccase in the fermented liquid reached to 238U/mL when added 0.01mg/mL oligosaccharin and cultivated for 10 days.That is 49.7% more than the contrast which no oligosaccharin was added.The laccase can accelerate the degradation of lignin,which have great effect on the growth of wood-rot fungi.Oligosaccharin can promote the growth of P.sp.by enhancing the activity of laccase.