Abstract: Objective To find the reason why vacuum tube can result in abnormal biochemical values and to investigate their countermeasures. Methods Serum was collected from 10 volunteers using five types of vacuum tube and 28 biochemical values were analyzed on a Hitachi 7600 automatic biochemical analyzer. EDTAK₂ anticoagulant blood（2μL,5μL,10μL,20μL and 50μL） was added respectively to 500μL whole blood from each volunteer. The influence of EDTAK₂ on the serum concentration of K⁺,Ca²⁺ and Mg²⁺ was observed. Results Compared with the separation gel tube,statistical differences were observed in 11 biochemical values obtained with coagulant tubes（P＜0.01）. Certain abnormal biochemical values were observed in coagulant and non-coagulant tubes. Conclusion Clinical nurses should carefully select vacuum tubes,selection of inappropriate vacuum tubes and incorrect blood sampling may lead to abnormal biochemical values.