Background: Severe pneumonia (SP) is a major complication of respiratory system diseases that is associated with high mortality and morbidity. If not treated correctly, it may rapidly lead to sepsis and multiple organ dysfunction syndrome. Despite continuous developments in antibiotic treatments for SP, the mortality rate remains high. Both basic and clinical research show that Xuebijing injection (XBJ) can improve the symptoms of SP. The aim of this study is to evaluate the effectiveness and safety of XBJ compared with placebo. Methods/design: This multicenter, blinded, randomized controlled trial will be conducted with a total of 700 participants with SP. Using a central randomization system, participants will be randomized (1: 1) into groups receiving either XBJ or placebo (within 24 h of diagnosis of SP) for 5-7 days with a 28-day follow-up. All participants will receive conventional treatment simultaneously. Both XBJ and placebo will be administered using a photophobic infusion set to avoid bias. The primary outcome is improvement of Pneumonia Severity Index risk rate. Adverse events will be monitored throughout the trial. Discussion: This is the first and largest randomized trial done in China on SP treatment using a Chinese herbal extract. In this trial, we will use central randomization and an electronic case report form, and we have designed an innovative blinding method for the traditional Chinese medicine injection. The results of this trial may help to provide evidence-based recommendations to clinicians for treatment of SP.