Abstract: With the continuous development of viscoelastic material, new types of viscoelastic dampers with improved dissipating performance and deformation performance have been put forward. But inevitably, they also loses linear characteristics at the same time. This paper introduces one type of hybrid nonlinear viscoelastic damper, and explores the characteristics of its nonlinearity. Then an accurate mechanical model, which considers its nonlinearity, is proposed and verified. The results indicate that there are five sources of nonlinearity, including the nonlinearity of phase difference which induces shape change of hysteretic curve, initial stiffness caused by large strain rate during the first loading, softening caused by temperature rise and fatigue performance, softening and hardening under large strain amplitude. The mathematical expression of the proposed mechanical model is concise with less parameters need to be identified. It can present a lot of nonlinear factors and features, such as heating-fatigue softening, ambient temperature dependency, softening and hardening under large strain. Therefore, the parameters are not need to be identified respectively under various cases. The hysteretic loops defined by the model agree well with the testing ones, so the model can simulate the nonlinear behavior of the hybrid nonlinear viscoelastic damper.