This study systematically investigated the nonlinear stress behavior of liquid crystal (8CB, 4-4'-n-octyl-cyanobiphenyl) in lamellar smectic A phase under large amplitude oscillatory shear (LAOS) flow. To investigate the nonlinear stress response under LAOS flow, the nonlinearity (I-3/1) from Fourier transform-rheology as a function of applied shear time (3600 s) was calculated according to changes in both strain amplitude gamma(0) and frequency omega. The storage modulus G'(t) and loss modulus G ''(t) from the conventional rheometer program under various LAOS flow conditions decreased and reached equilibrium as a function of time. This could be attributed to shear alignment of the lamellar smectic A structure. On the contrary, with G'(t) and G ''(t), the nonlinearity I-3/1(t) showed three different behaviors depending on the magnitude of strain amplitude: (1) Region I: Increased (increased and reached equilibrium), (2) region II: Increased and decreased (showed maximum value; decreased and reached equilibrium), and (3) region III: Decreased (decreased and reached equilibrium) as a function of time. These three different time-dependent behaviors of nonlinearity (I-3/1) were shown to be related with the alignment behavior of the lamellar structure. With stress decomposition method, the viscous and elastic stresses of 3600 s were calculated. Viscous and elastic stresses showed different behavior at region I and region III. With an equilibrium value of 3600 s, the G', G '', and nonlinearity (I-3/1) were plotted as a function of strain amplitude, gamma(0). Interestingly, I-3/1(gamma(0)) increased and then decreased (maximum) even though G'(gamma(0)) and G ''(gamma(0)) only decreased with increasing strain amplitude. From these results, it can be concluded that LAOS analysis of nonlinear stress, especially I-3/1 from FT-rheology, is more sensitive to microstructure than storage modulus G' and loss modulus G ''. (C) 2015 The Society of Rheology.