The relationship between relaxation and storage moduli has been studied using isotactic polypropylene(iPP) monofilaments. Relaxation and storage moduli are correlated by the coefficients of courier sine series. Since the theoretical equation of integral fiom is hard to manipulate, two moduli have been calculated numerically by convening it into flite power series. As the iPP is a semicrystalline polymer, the result of the theoretical calculation is compared with that of the experimental measurement within linear range. The equilibrium modulus due to on tanglements is used as the correction term. Polymeric material showed a linear behavior under the 2nd peak at the tangent modulus - strain curve and in the plateau region at the one-second tensile modulus - temperature curve. As the extension ratio and the temperature decrease, modulus calculated from the theoretical equation corresponds well to the modulus obtained by an experiment. By comparing experimental results with theoretical ones, it is clear that this theory can be applied to real polymeric materials in the linear range.