Objective To study the clinical application of dynamic monitoring of mainstream endtidal carbon dioxide in neonatal respiratory distress syndrome.Methods All of 23 premature neonates diagnosed with NRDS and placed on mechanical ventilation were admitted in this study.Their PetCO_2 was continuously monitored and paired with PaCO_2 at 112 different time points.The correlation between PetCO_2and PaCO_2 was compared.Results This study showed that the average PaCO_2 measured for 112 times was(38.2±5.6)mm Hg(1 mm Hg=0.133kPa)and the corresponding PetCO_2 was,(32.4±4.9)mm Hg;it also showed that PetCO_2 was positively correlated with PaCO_2 and PetCO_2 was even more closely correlated with PaCO_2 in infants with second degree of NRDS than in patients with third and fourth degree of NRDS.Conclusions Dynamically monitoring mainstream PetCO_2 is applicable in mechanically ventilated premature infants with NRDS,it can accurately reflect the level of PaCO_2;Thereby reducing the blood gas analysis,thus reducing the suffering of nursing workload and children.But it has limited significance in cases of severe NRDS.