The intestine is the most vulnerable target organ in septic patients and is the first to be damaged organ in multiple organ dysfunction syndrome(MODS).Therefore, improving intestinal motility and mucosal barrier function is critical to the treatment of sepsis. Many studies have shown that, early enteral nutrition(EN) in patients with sepsis helps prevent and treat intestinal dysfunction, reducing ICU mortality and length of stay in ICU. However, there is little research on feeding methods. In this study the investigators will compare the outcomes of different feeding methods: continuously-pumped in 24 hours, continuouslypumped in 16 hours and intermittently-pumped through the stomach tube. The aim of this study is to investigate the effects of different feeding methods on intestinal function in septic patients.