Objective To observe the in vitro antibacterial effect of compound Phellodendron phellodendron liquid coating on P. acnes and its clinical effect in the treatment of mild to moderate acne.Methods Basic experiment: The compound Phellodendron liquid coating was used as the experimental group, the benzoyl peroxide solution was used as the positive control group, the two were used as the combined group, and the sterilized normal saline was used as the negative control group to observe the inhibitory effect on P. acnes. Clinical trial: 120 patients with mild to moderate acne who were randomly selected in our hospital were divided into 2 groups, with 60 cases in each group, the experimental group was treated with compound Phellodendron liquid coating combined with benzoyl peroxide gel, and the control group was treated with benzoyl peroxide gel alone, and the effects of the two groups of patients before and after treatment were observed.Results Basic experimental studies showed that the minimum inhibitory concentration (MIC) of compound Phellodendron solution against Propionibacterium acnes was 150mg/ml, and the MIC of benzoyl peroxide solution with acetone as co-solvent was 0.002ug/ml. Clinical trials showed that the skin lesions in the experimental group had regressed significantly compared with those in the control group.Conclusion Compound Phellodendron liquid coating has a significant in vitro antibacterial effect on P. acnes, and the clinical effect on the treatment of acne is significant.