Recently, large amplitude oscillatory shear (LAOS) tests have been used to characterize and quantify nonlinear properties of complex fluids. At smaller strains, stress curve is sinusoidal shape similar to applied strain curve. At higher strains, however, stress curve is not sinusoidal any more. Therefore, several methods have been suggested to analyze the results from LAOS flow: (1) Lissajous-Bowditch curves, (2) G’, G” as a function of strain amplitude, (3) Fourier transformation, (4) Stress decomposition, (5) Chebyschev polynomials, (6) Dimensionless graphs. Among them, Fourier transformation (FT) rheology has been applied widely to various complex fluids because it is the most sensitive of the methods. In 2009, Hyun and Wilhelm defined a new nonlinear parameter Q and intrinsic nonlinearity Q0. They applied to monodisperse linear and comb-shaped polystyrene (PS) melts system. As a result, it was concluded that master curve of Q0 as a function of frequency displays the number of relaxation processes in different topological systems. In this study, it is objective to investigate the linear and nonlinear rheological properties of monodisperse PS solutions under small and large amplitude oscillatory shear flow. PS homopolymers with narrow polydispersities were dissolved in dioctyl phthalate (DOP) to determine the effect of polymer concentration. Master curves of linear and nonlinear rheological properties (G’, G”, and Q0) were obtained as a function of frequency and compared with each other. Furthermore, the results from monodisperse linear PS solutions were compared with those of bidisperse linear in solution. To analyze intrinsic nonlinearity Q0, MSF (Molecular Stress Function) model was also used.