Background: Acne vulgaris, a common skin disease, is a chronic inflammation of the pilocebaceous units these areas include the face, the upper part of the chest, and the back. Antibiotices that inhibit “propionibacterium acne” are the selective treatment for acne. Now, because of antibiotic resistant, treatment is less effective. Therefore finding the alternative cure is nessesary. Objectives: The goal of this study is the comparison of arnebia solution effect with placebo on the treatment of mild to moderate acne. Methods: This study has been designed as double blined clinical trial on 68 patients with mild to moderate acne. The patients were divided in two groups. Pregnant and milk-feeding women,childeren with the age less than 12 years and patients that received related drugs to acne have been excluded from this study .The groups were treated topically with arnebia and placebo solution two times per day for 8 weeks. The inflammatory and non inflammatory lesions and the side effects were assessed in both groups. Results: These finding show that the arnebia solution was decreased the inflammatory signs, significantly (p<0.001). In this period of time no adverse effect was seen. Conclusion: In conclusion the arnebia solution was effective in the treatment of mild to moderate acne.