Abstract: To develop proficiency testing samples for determination of Izod impact strength of plastics, and to evaluate the testing ability of laboratories for determination of Izod impact strength of plastics, according to the procedures prescribed in GB/T 1843-2008, ISO 180:2000 and CNAS (China National Accreditation Service for Conformity Assessment), the uniformity tests for samples were carried out on the basis of the guideline of S_S ≤ 0.3σ, and the stability tests for samples were carried out on the basis of the t-test method. The testing results of laboratories were evaluated by the Z-score method. The results show that:the uniformity and stability of proficiency testing samples were in conformity with the requirements; the statistical analysis on proficiency testing of Izod impact strength of 32 laboratories showed that there were 29 laboratories whose results were satisfied and 3 laboratories whose results were suspected or unsatisfied.