INTRODUCTION: Performing low-dose radiation therapy (LDRT) is a new approach to treat pneumonia resulting from COVID-19 disease. This paper aims to evaluate the effectiveness of LDRT in treating COVID-19 patients. METHODS: Medline was searched for "low-dose" and "radiation therapy" and "COVID-19" and "pneumonia" and "inflammation", to retrieve papers that published on low-dose radiation therapy to improve mortality of COVID-19 patients. Only clinical investigations that included original and case report papers were selected for this paper. RESULTS: The completed clinical trials that have performed LDRT to treat COVID-19 showed that the effectiveness of LDRT in treating COVID-19 was up to 90%. CONCLUSION: The vast majority of primary and secondary outcomes of clinical trial investigations regarding LDRT in treating COVID-19 found that LDRT can be considered a feasible treatment to improve mortality of COVID-19 patients.