Background: Type 2 diabetes mellitus patients complicated with infections experience severe vitamin D deficiency. High-dose vitamin D is applied to the treatment of corona virus disease 2019 (COVID-19) by some researchers, and good results have been achieved. However, the efficacy of vitamin D in the treatment of infections in COVID-19 patients with diabetes remains unclarified. This study aims to explore the effect of oral high-dose vitamin D in the treatment of diabetic patients with COVID-19. Methods: Randomized controlled trials about the application of high-dose vitamin D in the treatment of diabetic patients with COVID-19 will be retrieved from such electronic databases as Embase, PubMed, Cochrane Central Register of Controlled Trials, China National Knowledge Infrastructure database, Chinese Wanfang database and Chinese Biomedical Literature database. The retrieval time is from their inception to December 2020. According to the pre-designed inclusion/exclusion criteria, the data will be extracted independently by two researchers. The risk of bias of the included studies will be assessed by the Cochrane collaboration's tool. Meta-analysis will be conducted by using Revman 5.3 software. Results: A high-quality and comprehensive evaluation of oral high-dose vitamin D for the treatment of diabetic patients with COVID-19 will be made. Conclusion: The article will provide more convincing evidence and evidence-based guidance for clinical practice. Ethics and dissemination: The private information of individuals will not be made public, and this systematic evaluation will also not infringe on the rights of participants. Ethical approval is not required. Research results may be published in a peer-reviewed journal or disseminated in relevant conferences. PROSPERO Registration Number: CRD42020214284.