Based on a prestressed concrete girder with complex box-type section of 36m span, four models of 1/6 scale are made, and one of them is mixed with a kind of polymer latex. Experiments with monotonically and cyclically loading are carried out on the models to study bending fatigue behavior of the girder in service and under cyclic load exceeding the designed value, as well as the impact of polymer on fatigue performance of the girder. The results show that, under the cyclic load of value determined by the maximum and minimum stress at the key part of the girder in service, the fatigue performance is satisfactory and the fatigue behavior under a subsequent larger cyclic load is similar with that one under the same big cyclic load. Besides, the polymer has no negative effect on fatigue behavior of the model.