Background　End tidal carbon dioxide tension （PETCO2） monitoring has a lot of advantages like noninvasive， convenient， fast and intuitive， and it is widely used for monitoring the ventilation function. At the same time， PETCO2 is also associated with pulmonary perfusion well， so it can be used as a monitoring and evaluation index of heart function and circulation dynamics indirectly. That has been a good correlation between PETCO2 and arterial carbon dioxide tension（PaCO2）.　Objective　To summarize the factors may influence the correlation between PETCO2 and PaCO2， and to explore the pathophysiological mechanism may exist.　Content　We performed a review of the factors that affect the relativity between PETCO2 and PaCO2 from the operation's type， the basic condition of the patients and the aspect of anesthesia.　Trend　In general， there is a good correlation between PETCO2 and PaCO2 in normal condition， which has also been proved in corresponding physiological mechanism. However， the correlation between them still needs further research and exploration in a mixed more complex condition.