Abstract: This paper introduces the principle and method for determing the rheological behaviour of highly viscous materials.Not only can the apparent shear strain rates, and non-newtonian shear strain rates of the materials be determined thereby but also the flow indexes, stress indexes and apparent viscosities.The rheological properties of a polymer model material "M503", a mixture of half-and-half of XM-50 (a sealing material) and talc powder by weight are subjected to determination.The test results show that the M503 is a pseudoplatic material and that its stress indexes vary from 1.15 to 3.33 and the apparent viscosities range between 4.69×10⁷ and 0.99×10⁷Pa·s when the non-newtonian shearstrain rates are between 7.52×10⁵s^-1 and 105.56×10^-5s^-1.