To investigate the nonlinear viscoelastic response of E-glass fiber reinforced epoxy resin matrix composite, Schapery's model was used to describe the nonlinear viscoelasticity of composites, and the tensile creep/creep-recovery tests were carried out for [90]₁₆ transverse specimens and [±45]_4S shear specimens at different stress levels. According to the observed residual phenomena, a viscoplastic strain component was introduced into the Schapery's model and a method based on the analytical procedure for identifying the nonlinear viscoelastic parameters was proposed. The Schapery's nonlinear parameters g₀, g₁, g₂ and aσ were calculated, which are functions of the applied stress. The results show that the E-glass/epoxy composite exhibits obvious nonlinear viscoelasticity if the applied stress is higher than 53% of the tensile strength in transverse direction and 31% of the shear strength in the in-plan shear direction. In the transverse direction, the nonlinear parameters g_0T and g_2T are independent of stress, while g_1T increases linearly with stress, and a_σT decreases linearly with stress. In the in-plane shear direction, the nonlinear parameters g_0S and g_2S increase exponentially with stress, while g_1S increases linearly with stress, and a_σS decreases linearly with stress. Compared with the traditional nonlinear parameter identification method, the proposed method can obtain the relationship between nonlinear parameters and the applied stress conveniently and accurately.