Abstract:Paclobutrazole was a growth regulator and a fungicide，and its limited standard in bacteria was not clear.The effects of different concentrations of paclobutrazol 50，100，150，200，200，300 μg/mL on the dynamic residues and physiological and biochemical effects of paclobutil in Pleurotus ostreatus were investigated.The physiological and biochemical indexes included the weight loss rate of the fruiting body Content，soluble sugar content，malondialdehyde content，superoxide dismutase（SOD）and peroxidase（POD）enzyme activity.The results showed that 50 μg/mL paclobutrazol was applied to Pleurotus ostreatus and the residual amount was reduced to 0.5 μg/mL（MRL）after 2 days.Apply 150 μg/mL of paclobutrazol，residues were lower than the maxi mum residue after 5 days.At the same time，higher concentrationsof paclobutrazol （150 μg/mL and 200 μg/mL）had a certain effect on reducing the stability of physiological factors such as weight loss，maintenance nutrition and protective enzymes.In view of the above，paclobutrazol in Pleurotus ostreatus recommended concentration of not more than 150 μg/mL.