The incidence and mortality of acute respiratory distress syndrome (ARDS) are high. Patients with ARDS often need mechanical ventilation. Rational use of sedation and analgesia can improve the tolerance of patients with mechanical ventilation and reduce the lung injury caused by mechanical ventilation. Currently, the main sedative drugs used in clinical practice are midazolam, propofol and dexmedetomidine, but they all have disadvantages. It is urgent to find a sedative drug that can achieve rapid and sufficient sedation, does not inhibit breathing, leads to rapid recovery after drug withdrawal and does not increase incidence of delirium. Remimazolam besylate is a newly marketed ultra-short-acting GABAa receptor agonist, which is not metabolized by liver or kidney and is easily hydrolyzed by non-specific esterase in vivo. It has rapid effect, short recovery time, continuous infusion with almost no accumulation, little influence on respiration and circulation, and can be antagonized by flumasini. Compared with the above traditional sedatives, it has obvious advantages, especially suitable for sedation in ICU patients. There are few studies on remimazolam besylate used for sedation in ICU patients. At present, there is a lack of evidence-based medical evidence for the application of remazolam besylate in ICU patients. Its efficacy and safety, potential advantages and dominant population, application dose and combination of drugs still need to be further explored and clarified. The objective of this study was to investigate the sedative effects and advantages of remimazolam besylate versus midazolam in patients with ARDS requiring invasive mechanical ventilation. The successful undergoing of this study will provide practical basis for clinical sedation in patients with ARDS mechanical ventilation.