Abstract： Objective To discuss the clinical application of simplified neonatal critical illness score (sNCTS)in comparison with original neonatal critical illness score(oNCIS)published in 2001.Method A total of 705 neonates referred to neonate ICU(NICU)from 1 st January 2007 to 31th December 2009 were prospectively studied with control.The patients were scored by oNCIS on admission day,3rd,7th days after admission and on the day of discharge or dead.At the first scoring on admission,2 items of the PaO2 and pH were excluded from oNCIS's 10 items,and the remaining 8 items were used.Three items of plasma sodium,potassium and creatinine or BUN were scored out from 8 items and the still remained 5 items were used for the subsequent 3 scorings.The remaining 8 and 5 items were used as a simplified neonatal critical illness score.The simplified NCIS was evaluated by comparing the patients'condition that was assessed by the originat NCIS.The consistency rate between oNCIS and sNCIS should be over 80%.Results There were 8 items were used to evaluate the severity of disease on admission, and the consistence rate was 86.7%with the original NCIS.The 5 items selected from the original NCIS were used on the 3rd,the 7th days and the day of discharge or death.the consistence rate with original NCIS were 86.6%to 95.7%.A close correlation existed between the original NCIS and simplified NCIS(P<0.01).There were significant differences in mortality rates of the non-serious,serious and extremely serious groups between original NCIS and simplifled NCIS used for the first and the last seorings(P<0.01).Within a cohort of neonates with the same general condition,the assessments of mortality rates were not significantly different between these two methods (P>0.05).Conclusions Compared with the original NCIS.the simplified NCIS is consistent to a large extent in disease assessment,which is a concise way to evaluate the critical ill neonates objectively and can be easily applied to clinical practice.