System of a two-level atom interacting with two-mode cavity is considered in which two modes are coupled. Negativity is used to quantify the degree of entanglement. By means of numerical calculations, the evolution of the entanglement between atom and field or between two modes is investigated. The influence of coupling coefficient between two modes on the entanglement is discussed. The results show that the entanglement between atom and field or that between two modes displays periodic evolution, and its period is decreased with the increase of coupling coefficient between two modes. The entanglement between atom and field has a nonlinear relation with the increase of coupling coefficient between two modes. The entanglement between two modes is weakened with the increase of coupling coefficient between two modes.