Objective To study the correlation between ion concentrations of arterial and central venous blood in blood gas anal‐ysis .Methods This prospective study was performed in 72 patients with a central venous catheter and an artery catheter .A central venous blood sample and an artery blood sample were obtained at the same time after 10 minutes′anesthesia induction .Correlation analysis of the ion concentrations such as Na+ ,K+ ,Ca2+ between those in arterial and central venous blood were performed .The ion concentrations were determined by using GEM Premier 3000 Blood Gas Analysis System .Results The concentration value of Na+ in artery blood was (138 .81 ± 2 .40)mmol/L and in central venous blood was (139 .90 ± 2 .39)mmol/L ,there was significant difference between them(P<0 .01) .The concentration value of K+ in artery blood was (3 .92 ± 0 .42)mmol/L and in central venous blood was (3 .93 ± 0 .39)mmol/L ,which were not significantly different(P>0 .01) .The values of Ca2+ in artery blood was (1 .30 ± 0 .04)mmol/L and in central venous blood was (1 .32 ± 0 .05)mmol/L ,which were significantly different(P<0 .01) .Conclusion There is significant difference between Na+ ,Ca2+ concentrations in arterial blood gas analysis and those in central venous blood gas analysis ,central venous blood is relatively higher than artery blood ,while no statistically significant difference is observed for K+concentration .