Abstract: The CNAS T0381 proficiency testing program was summarized and was compared with the average result of 7 national plastics test centers in China. The result showed that 75 % of the laboratories were trustworthy on the test results of tensile stress at yield and tensile stress at 5 % strain tests, 68 % of the laboratories were trustworthy on the test results of tensile strain at yield test. The influencing factors on the test result, such as the pre-stress during grip, wrong operating of reset, and understanding of standards were also analyzed. It was found that the main factor was eliminating the pre-stress. The precision of equipment, understanding of standards, the working attitude should be improved.

Key words: proficiency testing, plastics, tensile property, yield