The fatigue behaviour of the welded beam-to-column connections of steel moment resisting frame in seismic area must be evaluated. The cohesive zone model is an efficient solution to study such connections by finite elements. It respects the energetic conservation and avoids numerical issues. A three-dimensional cohesive zone model element has been implemented in the home made finite element code Lagamine . It is coupled with the fatigue continuum damage model of Lemaître and Chaboche . The cohesive parameters are identified by the inverse method applied on a three points bending test modelling.