Objective: To observe the inhibition of Lianhua Qingwen capsule(LHQW) on Staphylococcus aureus biofilm(S.a BF). Method: Microdilution method was used to assay minimal bactericidal concentration (MBC) of LHQW and penicillin. The crystal violet(CV) and microbial activity (WST) assay were used to evaluate the inhibition of LHQW and penicillin on S.a BF. The scanning electron microscopy (SEM) and laser scanning confocal microscopy (CLSM) were used for observing S.a BF morphology and thickness measurement. Result: The MBC values of LHQW and penicillin against free S.a were 20 g·L-1 and 2 mg·L-1. Compared with the control group (control)

LHQW significantly inhabited S.a BF(P<0.05

P<0.01)

penicillin was no significant difference;S.a BF of the control group showed the thicker

normal bacterial form

dense overlay and the same size under the SEM

while S.a BF of LHQW group showed scattered colonies

inconsistent size

and S.a BF of penicillin group showed thicker

basically the same size

and the individual bacteria were collapse;S.a BF of control group were made of viable cells and a little dead bacteria under the CLSM

while S.a BF of LHQW group had a large number of dead bacteria

with which viable cells mixed;S.a BF of penicillin group was made of viable cells and the dead bacteria are distributed over the surface of S.a BF. Compared with the blank control group

S.a BF of LHQW group was thick significantly (P<0.01)

penicillin had no significant difference;Sa BF of LHQW group was less thick significantly than the penicillin group (P<0.01). Conclusion: LHQW has significant anti- S.a BF effect. Anti-S.a BF assessment system can be used in the antibacterial effect of traditional Chinese medicine.