Abstract: Objective To study the effect of different placed time for vacutainer and specimen on the results of emergency electrolyte detection. Methods With heparin lithium anticoagulation tube and common coagulation vacuum tube, electrolytes were detected at 30 minutes,one hour and two hours after extracting blood.ResultsAt 30 minutes and one hour after extracting blood,the levels of K⁺ and Na⁺ of the plasma group were significantly lower than those of the serum group (P<0.05). With the extension of specimen placed time, the levels of K⁺ and Na⁺ of the plasma group were becoming higher than those previously,and at two hours the difference had statistical significance (P<0.05). There was not obvious difference found in the levels of K⁺, Na⁺ and Cl^- of the serum group at different placed times(P>0.05). But the levels of CO₂ of both the plasma group and the serum group were significantly lower than those previously with the extension of specimen placed time,and the difference had statistical significance (P<0.05).Conclusion It is indicated that the using of different vacutainers effects electrolyte detection. With the extension of specimen placed time, the levels of K⁺ and Na⁺ of the plasma group increase gradually, and the levels of CO₂ of the plasma group and the serum group both decrease gradually.