In this paper， the effect of carvacrol to inhibit biofilm formation of E. faecalis R612-Z1 and the possible inhibition mechanisms were studied by analyzing the bacterial swimming and swarming abilities， the total bacterial counts and extracellular polysaccharides contents in biofilm， the changes of biofilm microstructure and the expression levels of related genes. The result of this study showed that the minimum inhibitory concentration of carvacrol to E. faecalis R612-Z1 was 512 μg/mL. The total bacterial counts in biofilm were not significantly changed after 1/4 MIC （128 μg/mL） carvacrol treatment， but the bacterial swimming and swarming abilities and exopolysaccharides contents in biofilm were meaningfully deceased. The biofilm structure became loose and rough， and membrane thickness was reduced after 1/4 MIC（128 μg/mL） carvacrol treatment observed by scanning electron microscopy and confocal laser scanning microscopy. Real-time PCR revealed that the expression levels of genes associated with adhesion and extracellular polysaccharide synthesis were significantly decreased after carvacrol treatment. This result indicated that carvacrol had a significant inhibitory effect on E. faecalis R612-Z1 biofilms by inhibiting initial adhesion and synthesis of extracellular polysaccharides of E. faecalis R612-Z1.