Abstract: Objective To evaluate the therapeutic effect of inhalation of vitamine B12 mixed solution in treating acute radiation-induced mucosal injury. Methods Totally 122 patients with acute radiation-induced mucosal injury resulting from radiotherapy were divided into two equal groups and received vitamine B12 mixed solution inhalation and gentamycin sulfate mixed solution inhalation, respectively. Results The patients receiving inhalation of vitamine B12 mixed solution showed favorable response to the treatment and the mucosal injury was alleviated as manifested by relieved pains, improved appetite and lessened body weight loss, which allowed uninterrupted administration of radiotherapy. In patients treated with inhalation of gentamycin sulfate mixed solution, by contrast, the mucosal injury was serious and in 8 patients radiotherapy had to be suspended for acute radiation-induced mucosal injury. Conclusion Vitamine B12 mixed solution inhalation can be an effective treatment for acute radiation-induced mucosal injury.