Abstract: Objective:To discuss the treatment of avoiding the different item's cross-contamination of automatic biochemical analyzer.Methods:There were divided into five groups:group A:the contents of alkaline phosphatase (ALP) in patients' serum with quality control serum were verified,then Mg²⁺ (magnesia ion) was verified;group B:firstly amylase (AMY) then Mg²⁺ were verified;matched group:just assess Mg²⁺;group C:the deionizer water was considered as sample,firstly assess the content of ALP in deionizer water,then assess Mg²⁺ ten times,afterward do the same processes which using quality control serum instead of deionizer water;group D:Use AMY instead of ALP,and do above-mentioned procedure.Results:Group A and group B the pollution rate were 9.93% and 10.13%.The cross-contamination was happened in assessment of Mg²⁺ as affected by reagent ALP and AMY.Conclusions:Medical technologists must be familiar with the manipulation and function of machines.When arranging the order of machines' testing items,it is needed to separate these items which has cross-contamination as far as possible.With the specific order,chemical pollution in different reagents can be reduced.