To observe clinical efficacy of trimetazidine combined with Yangxinshi Tablets in prevention and treatment of radiotherapy-related cardiac injury, and to explore its possible mechanism.Methods:A total of 72 patients receiving chest radiotherapy admitted in Tianjin People's Hospital from August 2017 to November 2018 were selected as study objects and randomly divided into control group, single-drug group and double-drug group, with 24 cases in each group.The control group was given routine radiotherapy.The single-drug group was given trimetazidine 20 mg each time since the beginning of radiotherapy, 3 times a day, until the end of radiotherapy.The double-drug group was given trimetazidine 20 mg each time since the beginning of radiotherapy, 3 times a day, combined with Yangxinshi Tablets 3 tablets each time, 3 times a day, until the end of radiotherapy.Before the radiotherapy, when the radiotherapy dose reached 30 Gy and 40 Gy, and at the end of radiotherapy, cardiac injury-related clinical manifestations were observed.Electrocardiogram, myocardial markers(cTnT, BNP and myocardial zymogram), malondialdehyde(MDA), superoxide dismutase(SOD)and interleukin-6(IL-6)were detected and their changes were observed.Results:Compared with the control group, there were significant differences in the drug groups in the improvement of clinical symptoms, electrocardiogram, echocardiography, myocardial markers and other clinical indicators, and in the changes of molecular mechanisms like SOD, MDA and IL-6.Conclusion:Trimetazidine combined with Yangxinshi Tablets can effectively prevent and treat heart injury during radiotherapy to a certain extent.It is safe and worthy of clinical application.The protective mechanism of Yangxinshi Tablets combined with trimetazidine for radiotherapy-induced cardiac injury may be related to alleviating oxidative stress and inflammatory reaction caused by radiation.