Background: Vasoplegia is vascular hyporesponsiveness to vasopressors and is an important phenomenon in children with refractory septic shock. This study aimed to develop an objective formula correlated with vasoplegia and evaluate the predictive power for mortality in children with refractory septic shock. Materials and Methods: We retrospectively analyzed children with refractory septic shock admitted to a pediatric intensive care unit (PICU) and monitored their hemodynamics via a pulse index continuous cardiac output (PiCCO) system. Serial hemodynamic data including cardiac index (CI), systemic vascular resistant index (SVRI) and vasoactive-inotropic score (VIS) were recorded during the first 72 hours after PICU admission. We defined vascular reactivity index (VRI) as SVRI/VIS and analyzed the effect of VRI in predicting mortality in children with refractory septic shock. Results: Thirty-three children with refractory septic shock were enrolled. The SVRI was lower in the mortality group compared to the survival group ( P < .05). The average area under the receiver operating characteristic curve of VRI within the first 72 hours was 0.8 and the serial values of VRI were significantly lower in the mortality group during the period from 0 to 48 hours ( P < .05). However, there were no significant differences in serial CI values between the survival and mortality groups. Conclusions: Vasoactive-inotropic score may potentially be used to quantify the severity of vasoplegia based on the clinical response of vessels after resuscitation with vasopressors. Lower VRI levels may indicate a higher risk of mortality in children with septic shock.