OBJECTIVE：To study the effect of isofla vaspidicacid PB （called PB for short ）on the biofilm adhesion and the gene expression of ergosterol metabolism related enzymes in Trichophyton rubrum . METHODS ：M38-A2 method was adopted to determine MIC of PB to T. rubrum . MTT assay was used to screen the biolfilm condition and initial adhesion period of T. rubrum . The effects of different concentrations of PB （40，80，160 µg/mL）on the adhesion duration of T. rubrum （growth control group without PB was set up ，similarly hereinafter ）were evaluated and the adhesion rate was calculated by using XTT assay ；the effects of different concentrations of PB （20，40，80 µg/mL）on the biofilm formation of T. rubrum at different initial adhesion periods （3，5，9 h）were observed and the adhesion rate was calculated by using XTT assay combined with inverted microscope ；qRT-PCR method was used to detect the effects of PB （320 µg/mL）on the mRNA expression of ergosterol metabolism related enzyme gene ERG6 and ERG11 in biofilm of T. rubrum . RESULTS ：MIC of PB to T. rubrum was 20 µg/mL. The biofilm of T. rubrum in RPMI-1640 medium containing 10％ FBS was the most metabolism activity at 6 h of initial adhesion. Compared with growth control group ，after treated with different concentrations of PB ，adhesion rate and mRNA expression of ERG6 and ERG11 in biofilm were decreased significantly （P＜0.01）. Hyphae decreased or even disappeared ，and the adhesion inhibition rate （at 5 and 9 h of initial adhesion ）increased significantly （P＜0.05 or P＜0.01）. CONCLUSIONS ：PB can inhibit the adhesion of T. rubrum and reduce the hyphae ；the mechanism may be associated with the inhibition of the biofilm adhesion and mRNA expression of ergosterol metabolism related enzyme gene ERG6 and ERG11.