Abstract: According to the procedures prescribed by GB/T 1633-2000, GB/T 8802-2001 and CNAS (China National Accreditation Service for Conformity Assessment), the proficiency testing for laboratory was carried out to evaluate the measurement ability of laboratory for Vicat softening temperature. The uniformity and stability tests for samples had been done on the basis of the guidelines of SS<0.3σ, the results showed that the uniformity and stability of samples were in conformity with the requirements. The test results of laboratories were evaluated by the Z score, the median value of results tested by each laboratory had been as the specified value of Vicat softening temperature, and the standardized interquartile range (NIQR) had been as the volatility measurement value (target standard deviation). There were 130 laboratories in proficiency testing, the results of 123 laboratories were satisfied, that of two was wrong and five was dissatisfied. Through the study on the project, the proficiency testing samples met the requirements of uniformity and stability were prepared, and the testing abilities for Vicat softening temperature of laboratories were evaluated by the appropriate statistical methods.