The temperature dependence of an exchange bias of the ferromagnetic hysteresis loop due to the ferromagnet – antiferromagnet interaction was investigated in the framework of Landau phenomenological phase transition theory. The two-layer system ferromagnet – antiferromagnet with uncompensated surface was considered for the case when the Neel temperature TN is close to and exceeds the Curie temperature TC and antiferromagnet has surface phase transition. Each layer has only one easy axis. They lie in the layer plane and are parallel to each other. In this case one can introduce one-component magnetic order parameter for each layer. The numerical modeling shows: the exchange bias on surface has different scenario of realization: – ferromagnet magnetic moment change sign smoothly; – ferromagnet magnetic moment change sign sharp and in vicinity of interface AFM has domen wall; – ferromagnet magnetic moment change sign sharp and in vicinity of interface AFM has not domen wall. It was found boundary these scenarios. Near TC the field HEB has minimum.