Abstract: Objective To evaluate the proficiency for iron and magnesium determination of labs in China with methods of external quality control.Methods The labs under the survey were divided into 3 groups(60 in each group).Split level design was used and lab proficiency was evaluated with robust statistical methods combined with expert comments.Results Totally 180 labs from 30 provinces(municipals and autonomous regions) participated in the proficiency test(PT).There were 70.56% of the labs(127) with satisfactory result,8.88%(16) with questionable result,and 20.56%(37) with dissatisfactory result.The rate of satisfactory result for construction sector was the highest(83.3%).The ratio of labs with satisfactory result for east area of China was 71.75%,71.42% for middle area,and 66.67% for west area.Conclusion Most labs participating in the PT had good competence in analyzing iron and magnesium.Rate of satisfactory result was not significantly different among the labs from 6 sectors.The proficiency for iron and magnesium determination of different areas was not significantly different.