Spontaneous shrinking of the second type of dumbbell domains (IID) subjected to both static bias field (Hb) and in-plane field (Hip) were investigated experimentally.It was found that this phenomenon depends on the amplitude,as well as the direction of Hip.In terms of a series of photographs,it was shown that the spontaneous shrinking of those IIDs perpendicular to Hip occurs earlier,and the spontaneous shrinking of those IIDs parallel to Hip occurs later.In addition,it was confirmed that IIDs lose a part of vertical Bloch lines (VBLs) in their walls in the process of spontaneous shrinking.