Substantial training effect in hysteresis loops was observed in ferromagnet (F)–antiferromagnet (AF) exchange coupled systems of the structure, Si(100)/iron–oxide(tAF)/F layer (5 nm)/Ta(10 nm), prepared by magnetron sputtering. The exchange bias field and the coercivity decrease with increasing number of loop cycles. The initially asymmetric hysteresis loop becomes more symmetric as the number of loop cycles increases. The effect is more prominent in the descending curve starting from the saturation in the positive (parallel to the pinned direction) direction than in the ascending curve of the hysteresis loop. The value of the ascending curve switching field |Hsw+| is rather unchanged while the switching field |Hsw−| in the descending curve decreases drastically with repeated hysteresis loop cycling as was observed in some CoO/Co and NiO/NiFe systems. Those phenomena can be interpreted by a modification of the extended model of Fulcomer and Charap’s: the essential modification being the introduction of positive and negative exchange coupling between AF grains.