Objective:To evaluate the relationship of vitamin D deficiency(VDD) between sepsis and septic shock among critical ill children, and investigate the influence of VDD on etiology and prognosis of sepsis.Methods:The observational cohort studies, involving vitamin D and critically ill children, were searched in Medline, Web of Science, EBSCO host and China National Knowledge Infrastructure, Wanfang Data Knowledge Service Platform.The quality assessment was conducted on the basis of the Newcastle-Ottawa Quality Assessment Scale.Consistent definitions of sepsis and septic shock were applied and standardized data were obtained following the study design.We retrieved the clinical outcomes related to septic shock and serum 25-hydroxyvitamin D 3concentrations and made a meta-analysis for the relation between VDD and clinical outcomes at two cut-offs. Results:In the analysis of collected data including severe VDD as a risk factor for incidence of sepsis and septic shock, the pooled RRwas 1.71(95% CI1.11 to 2.63, P=0.01) and 2.05(95% CI1.35 to 3.10, P<0.001) respectively, which were all higher compared with VDD.And severe VDD was also associated with cv-SOFA score( RR0.68, 95% CI0.45 to 0.91, P<0.001). However, no significant differences in mortality or the duration of vasopressor was found at severe VDD or VDD cut-off levels among septic shock patients. Conclusion:Among pediatric critical illness, severe VDD is more likely related to the incidence for sepsis and septic shock compared with VDD.And comorbidity with severe VDD could increase the cv-SOFA score of septic children.