Abstract: Objective: To study the difference of neuron specific enolase（NSE） level between serum and plasma,and the effect factors on NSE mensuration.Methods:To measure NSE level by using electrochemiluminescent principle and E170 automatic analyzer.Results: E170 system is very stable.There was no difference of NSE level between serum and plasma.It could make NSE level increased obviously if the sample was stored with blood cells together.Hemolysis could make NSE level increased very obviously,and there were 17.21 ng·mL^-1 NSE in per-gram hemoglobin.Conclusion: When measure NSE concentration,the samples must be detected immediately or the serum and plasma were separated from blood cells in 2 hours,and the samples must be avoided hemolysis in order to make sure the NSE result is correct.