Abstract： Objective： To observe the clinical effect of external application of Qingliang ointment in preventing phlebitis induced by intravenous infusion with mannitol. Methods：A total of 200 cases of inpatients who were treated with intravenous drip of mannitol were enrolled as the study objects， and were divided into the control group and the experiment group according to the random number table method，100 cases in each group. Local wet-hot compress with magnesium sulphate on transparent dressing was carried out in the control group， started from the starting point of intravenous puncture and following vascular direction. The experiment group was given external application of Qingliang ointment of Chinese medicine. The incidence of phlebitis，the pain level during intravenous drip，and the satisfaction of patients were compared between the two groups. Results：The incidence of phlebitis was 10.00% in the experiment group，and 26.00% in the control group， the difference being significant(P＜0.05). The incidence of pain during intravenous drip was 18.00% in the experiment group， and 95.00% in the control group，the difference being significant(P＜0.05). The satisfaction was 98.00% in the experiment group，and 82.00% in the control group，the difference being significant(P＜0.05). Conclusion：During intravenous drip of mannitol，the external application of Qingliang ointment，in comparison with wet-hot compress with magnesium sulphate， can more effectively prevent the occurrence of phlebitis and relieve pain with high satisfaction of patients.