Objective To analyse the clinical situations and other factors that influence the PetCO2 monito-ring. The analysis can improve the nursing care for mechanical ventilated patients. Methods To retrospectively ana-lyze 212 PetCO2 monitoring ntanbers and capnograms in 108 mechanical ventilated patients. Results PetCO2 abnor-malities rate was 13.4%; leakage in the ventilator system was 30.4%; endotracheal tube malposition 6.8%; endo-tracheal tube baloon leakage 11.3%; secreations 22.4%; hyperventilation 12.5%; hypopeffusion 7.6%; hypoper-fusion of the lung 5.8%; mechanical malfunctioning 3.2%. Conclusions Continue monitoring of PetCO2 and cap-nogram along with hemodynamic monitoring in mechanical ventilated patients can timely find patients' problems and promptly use appropriate interventions. The understanding of these monitoring systems can improve the quality of the nursing care for the critically ill patients.