A nonlinear Tavis-Cummings model describing interaction of two atoms with a single mode nonlinear field is presented. The relation between it and other cavity quantum electrodynamics (QED) model is analyzed. Berry phase and eigenvalues of this quantum system are evaluated explicitly, and how they change with system parameters is studied by numerical simulation. The results show that they relate to the dipole-dipole coupling strength between two atoms and atom-field coupling constant and nonlinear coefficient of field. Besides, the influence on Berry phase of nonlinear coupling effect increases with the addition of the number of the photon.