Objective To observe the effect of ozone hydrotherapy on patients with scalp seborrheic dermatitis. Methods Totally 120 patients of scalp seborrheic dermatitis were randomly divided into a research group and a control group, each group had 60 cases. The patients in the research group were treated with ozone hydrotherapy, and the patients in the control group were treated with 2% Ketoconazole lotion. The clinical symptom scores, recurrence rate and sebum level before and after treatment were compared between the two groups. Results The downward trends of the symptom scores in the research group were more significant than those in the control group (P < 0.05). The total effective rates in the research group after treatment for 2 and 4 w were markedly higher than those in the control group (P < 0.05). Sebum level of the research group decreased more significantly than that of the control group (P < 0.05). The recurrence rate of the research group was markedly lower than that of the control group (P < 0.05). Conclusions Ozone hydrotherapy can significantly improve the clinical efficacy of scalp seborrheic dermatitis, reduce the rate of clinical relapse.