Sepsis is an inflammatory syndrome with life-threatening organ dysfunction resulting from a dysregulated host response to infection. Although the treatment for sepsis has improved a lot in the last 30 years, sepsis related mortality remains high. In the recent 10 years, high dose intravenous injection of vitamin C, the first line antioxidant of human, has received more and more attention in the field of critical care, its beneficial effect has been demonstrated by several small scale clinical trial and animal studies, but the effect of high dose vitamin C on sepsis in a larger trial seems warranted in further study. Here we will conduct a prospective, multi-center, double-blind, adaptive sample size, randomized, placebo-controlled, clinical trial named as HDVCIS. The trial protocol has been approved by Clinical Trail Ethics Committee of Ruijin Hospital of Shanghai JiaoTong University School of Medicine. This trial has been registered in Chinese Clinical Trial Registry (ChiCTR1800017633) in August 7, 2018. Patients will be recruited from 4 medical centers in China. Its object is to testify the efficacy and safety of high dose vitamin C in the treatment of sepsis.