Abstract: The pellets of polyethylene pipe material were selected as samples, then the particle size was screened. In accordance with the method in CNAS-GL03, the homogeneity and stability of samples were tested, and the testing data was fixed. According to the requirements of the method in GB 3359-1982, the statistical tolerance interval of a single measurement was given. The results showed that the nominal viscosity values of polyethylene pipe material for internal quality control sample in laboratory were (2 140.13 ± 41.84) Pa·s.