Severe sepsis and septic shock remain the leading causes of child mortality worldwide. Sepsis is a complex process that ultimately leads to circulation disorders, organ perfusion abnormalities, capillary leakage, tissue hypoxia, and organ failure. The difficulty of clinical treatment is microcirculation and mitochondrial dysfunction in septic shock. Once shock enters the stage of microcirculation failure, conventional treatment is ineffective. ECMO can effectively support the circulatory system and provide good oxygen delivery, but there are many controversies in clinical treatment. 1) whether ECMO can effectively improve the clinical prognosis of children with septic shock; 2) appropriate timing for ECMO intervention; 3) which key clinical factors affect the effect of ECMO treatment. This study intends to adopt a multi-center, prospective, non-randomized controlled trial design, and the main research hypothesis is whether ECMO treatment can improve the success of discharge survival of children with septic shock.