Tigecycline as representative glycylcycline antibiotics, has wide antibacterial spectrum and strong antibacterial activity, tigecycline in almost all of the gram positive bacteria and most gram negative bacteria and atypical pathogens, anaerobic bacteria are very good antibacterial activity except Pseudomonas aeruginosa, Proteus. Safety on organ function, in patients with renal insufficiency or in dialysis patients, no dose adjustment is required application of tigecycline, mild to moderate hepatic insufficiency patients do not need to adjust the dose of tigecycline. Piperacillin / tazobactam also is a broad spectrum, potent antibiotics, especially strong bactericidal activity against Pseudomonas aeruginosa, including resistant enzyme producing gram negative bacilli, in accordance with its pharmacokinetic pharmacodynamic characteristics of prolonged infusion time can obtain a stronger bactericidal activity. These two potent drugs have broad antimicrobial spectrum, strong bactericidal activity, and provide for the treatment of severe sepsis and septic shock a new choice in antibiotic selection, to a certain extent reduces the resistance pressure, and have more clinical safety.